KR102402529B1 - Mechanisms for Reduced Density CSI-RS - Google Patents

Abstract

According to some embodiments, a method for use in a network node transmitting channel state information reference signals (CSI-RSs) comprises: providing an indication of a subset of PRBs that a wireless device should use to measure the CSI-RS to the wireless transmitting to the device; and transmitting the CSI-RS on the indicated subset of PRBs. According to some embodiments, a method for use in a wireless device receiving a CSI-RS comprises: receiving an indication of a subset of PRBs that the wireless device should use to measure a CSI-RS associated with an antenna port; and receiving the CSI-RS on the indicated subset of PRBs. In some embodiments, the indication of the subset of PRBs that the wireless device should use to measure the CSI-RS includes a density value and a comb offset.

Description

Mechanisms for Reduced Density CSI-RS

Specific embodiments relate to wireless communication, and more particularly, to mechanisms for reduced density channel state information reference signal (CSI-RS).

Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) uses Orthogonal Frequency Division Multiplexing (OFDM) in the downlink, where each downlink symbol may be referred to as an OFDM symbol, In the uplink, Discrete Fourier Transform (DFT)-spread OFDM is used, where each uplink symbol may be referred to as an SC-FDMA symbol. The basic LTE downlink physical resources include the time-frequency grid shown in FIG. 1 .

Next-generation mobile wireless communication systems (5G or NR) support a diverse set of use cases and a diverse set of deployment scenarios. The latter includes deployment at both low frequencies (hundreds of MHz), similar to today's LTE, and very high frequencies (mm-wave of tens of GHz). At high frequencies, propagation characteristics make it difficult to achieve good coverage. One solution to the coverage problem is to use high-gain beamforming, typically in analog fashion, to achieve a satisfactory link budget. Beamforming can also be used at lower frequencies (typically digital beamforming) and is expected to be essentially similar to the already standardized 3GPP LTE system (4G).

1 shows an exemplary downlink radio subframe. The horizontal axis represents time and the other axis represents frequency. The radio subframe 10 includes a resource element 12 . Each resource element 12 corresponds to one OFDM subcarrier during one OFDM symbol period. In the time domain, LTE downlink transmission may be organized into radio frames.

이 도시되어 있지만, 상이한 서브캐리어 간격 값들이 NR에서 지원된다. NR에서 지원되는 서브캐리어 간격 값(상이한 수비학이라고도 함)은

에 의해 주어지며, 여기서 α는 음이 아닌 정수이다.LTE and NR use OFDM in the downlink and DFT-spread OFDM or OFDM in the uplink. Accordingly, the basic LTE or NR downlink physical resource can be viewed as a time-frequency grid as shown in FIG. 1 , where each resource element corresponds to one OFDM subcarrier during one OFDM symbol period. 1 shows the subcarrier spacing

Although shown, different subcarrier spacing values are supported in NR. Subcarrier spacing values supported in NR (also known as different numerology) are

, where α is a non-negative integer.

의 수비학에 대한 슬롯 지속시간은 슬롯 당 14개의 OFDM 심볼을 취하는

ms로 주어지며, 서브프레임 당 슬롯의 수는 수비학에 의존한다.2 shows an example radio frame. The radio frame 14 includes a subframe 10 . In LTE, each radio frame 14 is 10 ms and consists of 10 equally sized subframes 10 with a length of Tsubframe = 1 ms. In LTE, in the case of normal periodic prefix, one subframe consists of 14 OFDM symbols and the duration of each symbol is about 71.4 μs. In NR, the subframe length is fixed at 1 ms regardless of the numerology used. In NR,

The slot duration for the numerology of

Given in ms, the number of slots per subframe depends on the numerology.

A user is assigned a specific number of subcarriers for a predetermined amount of time. These are referred to as physical resource blocks (PRBs). Thus, PRB has both time and frequency dimensions. In LTE, a resource block corresponds to one slot (0.5 ms) in the time domain and 12 consecutive subcarriers in the frequency domain. Resource blocks are numbered in the frequency domain, starting with 0 at one end of the system bandwidth. For NR, a resource block is also 12 subcarriers in frequency, but may span more than one slot in the time domain.

Downlink transmission is dynamically scheduled, that is, in each subframe, the base station transmits control information about a terminal to which data is to be transmitted and a resource block to which data is to be transmitted in the current downlink subframe. In LTE, control signaling is typically sent in the first 1, 2, 3 or 4 OFDM symbols in each subframe.

3 shows an exemplary downlink subframe. Subframe 10 includes reference symbols and control signaling. In the example shown, the control region includes three OFDM symbols. The reference symbol includes cell specific reference symbols (CRS) capable of supporting a plurality of functions including fine time and frequency synchronization and channel estimation for a predetermined transmission mode.

LTE includes multiple physical downlink channels. A downlink physical channel corresponds to a set of resource elements carrying information from higher layers. The following are some of some physical channels supported in LTE: Physical Downlink Shared Channel (PDSCH); Physical Downlink Control Channel (PDCCH); Enhanced Physical Downlink Control Channel (EPDCCH); Physical Uplink Shared Channel (PUSCH); and Physical Uplink Control Channel (PUCCH).

PDSCH is mainly used to carry user traffic data and higher layer messages. The PDSCH is transmitted in a downlink subframe outside the control region as shown in FIG. 3 . Both the PDCCH and the EPDCCH are used to convey Downlink Control Information (DCI) such as PRB allocation, modulation level and coding scheme (MCS), and a precoder used in the transmitter. The PDCCH is transmitted in the first 1 to 4 OFDM symbols in the downlink (ie, in the control region), whereas the EPDCCH is transmitted in the same region as the PDSCH.

LTE defines different DCI formats for downlink and uplink data scheduling. For example, DCI formats 0 and 4 are used for uplink data scheduling, whereas DCI formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 2D, 3/3A are used for downlink data scheduling. used Two search spaces (ie, a common search space and a UE-specific search space) are defined for the PDCCH.

The common search space consists of PDCCH resources on which all user equipments (UEs) monitor PDCCH(s). A PDCCH intended for all UEs or a group of UEs is always transmitted in a common search space so that all UEs can receive it.

The UE-specific search space consists of PDCCH resources that may vary from UE to UE. The UE monitors both the common search space and the UE-specific search space associated with it for the PDCCH(s). Since DCI 1C carries information on PDSCH for all UEs or UEs to which Radio Network Temporary Identifiers (RNTIs) are not allocated, they are always transmitted in a common search space. DCI 0 and DCI 1A may be transmitted in a common or UE-specific search space. DCI 1B, 1D, 2, 2A, 2C and 2D are always transmitted in the UE-specific search space.

In the downlink, which DCI format is used for data scheduling is related to the downlink transmission scheme and/or the type of message to be transmitted. The following are some of the transmission schemes supported in LTE: single-antenna port; transmit diversity (TxD); open-loop spatial multiplexing; closed-loop spatial multiplexing; Up to 8 layers of transport.

The PDCCH is always transmitted in a single-antenna port or TxD scheme, whereas the PDSCH may use any one of the transmission schemes. In LTE, the UE is configured in a transmission mode (TM), not in a transmission mode. There are 10 TMs (ie, TM1 to TM10) defined for PDSCH in LTE. Each TM defines a primary transmission scheme and a backup transmission scheme. The backup transmission method is a single antenna port or TxD. The main transmission methods of LTE include: TM1: single antenna port, port 0; TM2: TxD; TM3: open-loop SM; TM4: closed-loop SM; TM9: up to 8 layer transport, ports 7 to 14; TM10: Up to 8 layer transport, ports 7 to 14.

In TM1 to TM6, a cell-specific reference signal (CRS) is used as a reference signal for both channel state information feedback and demodulation at the UE. In TM7 to TM10, a UE-specific demodulation reference signal (DMRS) is used as a reference signal for demodulation.

LTE includes codebook-based precoding. Multi-antenna technology can significantly increase the data rate and reliability of wireless communication systems. Performance is particularly improved if both the transmitter and receiver are equipped with multiple antennas, creating a multiple input multiple output (MIMO) communication channel. Such systems and/or related technologies are often referred to as MIMO.

A core component of LTE is MIMO antenna placement and support of MIMO-related technologies. Currently, up to 8-layer spatial multiplexing with 2, 4, 8 and 16 1D transmit (Tx) antenna ports and 8, 12 and 16 Tx 2D antenna ports is supported in LTE with channel dependent precoding. Spatial multiplexing mode targets high data rates in favorable channel conditions. 4 illustrates an exemplary spatial multiplexing operation.

4 is a block diagram illustrating a logical structure of a precoded spatial multiplexing mode in LTE. The information carrying symbol vector s is multiplied by an N _T × r precoder matrix W , which serves to distribute the transmit energy in a subspace of the N _T dimensional vector space (corresponding to the N _T antenna ports). becomes

The precoder matrix is typically selected from a codebook of possible precoder matrices, and typically is a precoder matrix indicator (PMI) that specifies a unique precoder matrix in the codebook for a given number of symbol streams. is indicated by Each of the r symbols of s corresponds to one layer and r is referred to as a transmission rank. Spatial multiplexing is achieved because multiple symbols can be transmitted simultaneously on the same time/frequency resource element (TFRE). The number r of symbols is typically adapted to fit the current channel properties.

LTE uses OFDM in the downlink (and DFT precoded OFDM in the uplink). The received N _R ×1 vector y _n for a given TFRE on subcarrier n (or alternatively the number of data TFREs n) is modeled as

where e _n is the noise/interference vector. Precoder W may be a wideband precoder, constant or frequency selective with respect to frequency.

The precoder matrix is often chosen to match the properties of the N _R xN _T MIMO channel matrix H _n , which may be referred to as channel dependent precoding. This is also often referred to as closed-loop precoding, and essentially attempts to concentrate the transmitted energy into a subspace that can be said to be strong in the sense of delivering a significant portion of the transmitted energy to the UE. In addition, the precoder matrix can also be chosen to orthogonalize the channels, which means that, after proper linear equalization at the UE, inter-layer interference is reduced.

The transmission rank, and thus the number of layers spatially multiplexed, is reflected in the number of columns of the precoder. For efficient performance, the transmission rank may be chosen to match the channel properties.

MIMO includes single-user MIMO and multi-user MIMO. Transmitting all data layers to one UE is referred to as single-user MIMO (SU-MIMO). Transmitting data layers to multiple UEs is referred to as multi-user MIMO (MU-MIMO).

MU-MIMO is, for example, when two UEs are located in different areas of a cell so that they can be separated via different precoders (or beamforming) at a base transceiver station (BTS), i.e., a base station (BS). It is possible. Two UEs may be served on the same time-frequency resource (ie, PRB) by using different precoders or beams.

In Demodulation Reference Signal (DMRS) based transmission modes TM9 and TM10, different DMRS ports and/or the same DMRS port with different scrambling codes may be assigned to different UEs for MU-MIMO transmission. In this case, MU-MIMO is transparent to the UE (ie, the UE is not informed about the joint scheduling of other UEs in the same PRB). MU-MIMO requires more accurate downlink channel information than SU-MIMO for the eNB to use precoding to separate UEs (ie, to reduce cross-interference for co-scheduled UEs).

LTE includes codebook-based channel state information (CSI) estimation and feedback. In closed loop MIMO transmission schemes such as TM9 and TM10, the UE estimates downlink CSI and feeds it back to the eNB. The eNB transmits downlink data to the UE using the feedback CSI. CSI consists of a transmission rank indicator (RI), a precoding matrix indicator (PMI) and a channel quality indicator(s) (CQI).

The codebook of precoding matrices is used by the UE to find the best match between the estimated downlink channel H _n and the precoding matrix in the codebook based on a predetermined criterion (eg, UE throughput). Channel H _n is estimated based on a non-zero power CSI reference signal (NZP CSI-RS) transmitted in the downlink for TM9 and TM10.

CQI/RI/PMI together provide the downlink channel status to the UE. This is also referred to as implicit CSI feedback because the estimate of H _n is not fed back directly. CQI/RI/PMI may be wideband or partialband depending on the configured reporting mode.

The RI corresponds to the recommended number of streams that must be spatially multiplexed and transmitted in parallel over the downlink channel. The PMI identifies (in a codebook containing a number of precoders equal to the number of CSI-RS ports) a recommended precoding matrix codeword for transmission, related to the spatial characteristics of the channel. CQI indicates the recommended transport block size (i.e. code rate), LTE is one or two simultaneous (on different layers) transmission of transport blocks to the UE in one subframe (i.e. separately encoded information blocks). Thus, there is a relationship between the CQI and the signal-to-interference and noise ratio (SINR) of the spatial stream(s) in which the transport or blocks are transmitted.

LTE defines a codebook of up to 16 antenna ports. Both one-dimensional (1D) and two-dimensional (2D) antenna arrays are supported. For LTE Rel-12 UE and earlier, only codebook feedback for 1D port layout is supported, with 2, 4 or 8 antenna ports. Accordingly, the codebook is designed assuming that the ports are arranged on a straight line. In LTE Rel-13, the codebook for 2D port layout was specified for the case of 8, 12 or 16 antenna ports. In addition, LTE Rel-13 also specified the codebook 1D port layout for the case of 16 antenna ports.

LTE Rel-13, class A and class B, includes two types of CSI reporting: In class A CSI reporting, the UE is based on a new codebook for a configured 2D antenna array using 8, 12 or 16 antenna ports. to measure and report CSI. CSI, similar to the CSI report of pre Rel-13, consists of RI, PMI, and CQI or CQIs.

In class B CSI reporting, in one scenario (referred to as “K>1”), the eNB may preform multiple beams in one antenna dimension. On other antenna dimensions there may be multiple ports (1, 2, 4 or 8 ports) within each beam. Beamformed CSI-RS is transmitted along each beam. The UE first selects the best beam from a configured group of beams, and then measures the CSI in the selected beam based on the legacy codebook for 2, 4 or 8 ports. Then, the UE again reports the selected beam index and CSI corresponding to the selected beam.

In another scenario (called "K=1"), the eNB can form up to four (2D) beams on each polarization and the beamformed CSI-RS is transmitted along each beam. The UE measures the CSI for the beamformed CSI-RS and feeds back the CSI based on the new class B codebook for 2, 4, 8 ports.

LTE supports two types of CSI feedback: periodic feedback and aperiodic feedback. In periodic CSI feedback, the UE is configured to report CSI periodically on certain preconfigured subframes. Feedback information is carried on the uplink PUCCH channel.

In aperiodic CSI feedback, the UE reports CSI only when requested. The request is signaled on the uplink grant (ie either in DCI 0 or DCI 4 carried on PDCCH or EPDCCH).

LTE Release-10 includes a new reference symbol sequence for estimating channel state information called non-zero power (NZP) CSI-RS. The NZP CSI-RS provides several advantages over being based on CSI feedback on cell-specific reference symbols (CRS), which were used for this purpose in previous releases.

As an example, the NZP CSI-RS is not used for demodulation of the data signal, and therefore does not require the same density (ie, the overhead of the NZP CSI-RS is substantially less). As another example, NZP CSI-RS provides a more flexible means of configuring CSI feedback measurement (eg, the NZP CSI-RS resource to measure may be configured in a UE-specific manner). By measuring with respect to the NZP CSI-RS, the UE can estimate the effective channels traversed by the NZP CSI-RS, including radio propagation channels and antenna gains.

Up to 8 NZP CSI-RS ports can be configured for LTE Rel-11 UE. The UE can estimate the channel from up to 8 transmit antenna ports in LTE Rel-11. Up to LTE Rel-12, NZP CSI-RS uses an orthogonal cover code (OCC) of length 2 to overlay two antenna ports on two consecutive REs. OCC may be called code division multiplexing (CDM) interchangeably.

Many different NZP CSI-RS patterns are available. Examples are shown in FIG. 5 .

5 shows a resource element grid with resource block pairs indicating potential locations for CSI-RS in case of 2, 4 and 8 antenna ports. Each resource element grid represents one PRB 16 . The horizontal axis represents the time domain and the vertical axis represents the frequency domain.

For two CSI-RS antenna ports, FIG. 5 shows 20 different patterns (ie, 20 pairs of resource elements labeled 0 and 1) within a subframe. One exemplary pattern is indicated by hatching.

For 4 CSI-RS antenna ports, the number of corresponding patterns is 10 (ie, 10 groups of resource elements labeled 0 to 3, where resource element pairs 0 and 1 in the same group, and resource Element pairs 2 and 3 are separated by 6 resource elements in the frequency domain). One exemplary pattern is shown in hatching.

For 8 CSI-RS antenna ports, the number of corresponding patterns is 5 (ie, 5 groups of resource elements labeled 0-7, where resource element pairs 0 and 1 in the same group and resource Element pairs 2 and 3 are separated by 6 resource elements in the frequency domain, and resource element pairs 4 and 5 and resource element pairs 6 and 7 in the same group are separated by 6 resource elements in the frequency domain) . One exemplary pattern is shown in hatching.

The example shown is for frequency division duplex (FDD). For time division duplex (TDD), an additional CSI-RS pattern may be used.

The reference signal sequence for CSI-RS is defined as follows in section 6.10.5.1 of 3GPP TS 36.211

는 라디오 프레임 내의 슬롯 수이고

은 슬롯 내의 OFDM 심볼 수이다. 의사-랜덤 시퀀스

는 각각 3GPP TS 36.211의 섹션 7.2 및 6.10.5.1에 따라 생성되고 초기화된다. 또한, 수학식 2에서,

은 3GPP TS 36.211에 의해 지원되는 가장 큰 다운링크 대역폭 구성이다.here

is the number of slots in a radio frame

is the number of OFDM symbols in a slot. pseudo-random sequence

are generated and initialized according to sections 7.2 and 6.10.5.1 of 3GPP TS 36.211, respectively. Also, in Equation 2,

is the largest downlink bandwidth configuration supported by 3GPP TS 36.211.

In LTE Rel-13, the NZP CSI-RS resource has been extended to include 12 ports and 16 ports. These Rel-13 NZP CSI-RS resources are three legacy 4-port CSI-RS resources (to form a 12-port NZP CSI-RS resource) or two legacy (to form a 16-port NZP CSI-RS resource). It is obtained by aggregating 8-port CSI-RS resources. All aggregated NZP CSI-RS resources are located in the same subframe. Examples of forming 12-port and 16-port NZP CSI-RS resources are shown in FIGS. 6A and 6B, respectively.

6A and 6B show a resource element grid with resource block pairs indicating potential locations for CSI-RS for 12 and 16 antenna ports, respectively. The horizontal axis represents the time domain and the vertical axis represents the frequency domain.

6A shows an example of aggregating three 4-port resources to form a 12-port NZP CSI-RS resource. Each resource element of the same 4-port resource is labeled with the same number (eg, 4 resources labeled 1 form one 4-port resource, and 4 resources labeled 2 are the second 4 - Form a port resource, and 4 resources labeled with 3 form a third 4-port resource). Together, the three aggregated 4-port resources form a 12-port resource.

6B shows an example of aggregating two 8-port resources to form a 16-port NZP CSI-RS resource. Each resource element of the same 8-port resource is labeled with the same number (eg, 8 resources labeled 1 form one 8-port resource, 8 resources labeled 2 form the second 8 - to form a port resource). Together, the two aggregated 8-port resources together form a 16-port resource.

In a given subframe, 3 12-port resource configurations (ie 9 out of 10 4-port resources used) and 2 16-port resource configurations (ie 4 out of 5 8-port resources used) This is possible. The following port numbering is used for the aggregated NZP CSI-RS resource. In the case of 16 NZP CSI-RS ports, the aggregated port numbers are 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 and 30. In the case of 12 NZP CSI-RS ports, the aggregated port numbers are 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 and 26.

In addition, the Rel-13 NZP CSI-RS design supports two different OCC lengths. Multiplexing the antenna ports is possible using OCC lengths 2 and 4 for both 12-port and 16-port NZP CSI-RS. Until Release 13 of LTE, CSI-RS is transmitted in all PRBs of the system bandwidth at a density of 1 RE/port/PRB.

An example of using OCC length 2 is shown in FIGS. 7 and 8 . An example of using OCC length 4 is shown in FIGS. 9 and 10 .

7 shows a resource element grid in an exemplary NZP CSI-RS design for 12 ports with an OCC length of 2. Different 4-port NZP CSI-RS resources are indicated by letters A-J. For example, 4-port resources A, F and J may be aggregated to form a 12-port NZP CSI-RS resource. Length 2 OCC is applied across two resource elements with the same subcarrier index and adjacent OFDM symbol indices (e.g., OCC 2 is applied to resource elements with OFDM symbol indexes 5-6 and subcarrier index 9 of slot 0) applies).

8 shows a resource element grid in an exemplary NZP CSI-RS design for 16 ports with an OCC length of 2. Different 8-port NZP CSI-RS resources are indicated by numbers (eg 0-4). A resource pair containing an 8-port resource is indicated by a letter (eg, A-D). For example, resource pairs A0, B0, C0 and D0 form one 8-port NZP CSI-RS resource. Resource pairs A3, B3, C3 and D3 form another 8-port NZP CSI-RS resource. 8-port NZP CSI-RS resources 0 and 3 may be aggregated to form a 16-port NZP CSI-RS resource, for example. Length 2 OCC is applied across two resource elements with the same subcarrier index and adjacent OFDM symbol indices (e.g., OCC 2 is applied to the resource element with OFDM symbol index 2-3 and subcarrier index 7 of slot 1) applies).

의, 안테나 포트 p의 기준 심볼로서 이용되는 복소값 변조 심볼

로의 맵핑은 다음과 같이 정의된다 : For OCC length 2 (i.e. upper layer parameter 'cdmType' is set to cdm2 or 'cdmType' is not configured by Evolved Universal Terrestrial Access Network (EUTRAN) - see 3GPP TS 36.331 for details), math Reference signal sequence in Equation 2

A complex value modulation symbol used as a reference symbol of the antenna port p of

The mapping to is defined as:

here

는 다운링크 전송 대역폭을 나타낸다; 인덱스 k' 및 l'는 (각각의 PRB의 하단으로부터 시작하는) 서브캐리어 인덱스 및 (각각의 슬롯의 우측으로부터 시작하는) OFDM 심볼 인덱스를 나타낸다. 상이한 (k', l') 쌍들의 서로 다른 CSI-RS 자원 구성들로의 맵핑이 표 1에 주어진다. OCC 길이가 2인 경우의 양 p'는, 다음과 같이 안테나 포트 번호 p와 관련된다 :In Equation 3 and Equation 4,

denotes the downlink transmission bandwidth; The indices k' and l' indicate the subcarrier index (starting from the bottom of each PRB) and the OFDM symbol index (starting from the right side of each slot). The mapping of different (k', l') pairs to different CSI-RS resource configurations is given in Table 1. The quantity p' when the OCC length is 2 is related to the antenna port number p as follows:

● p = p' (in case of CSI-RS using up to 8 antenna ports)

● If the upper layer parameter 'cdmType' is set to cdm2 for CSI-RS using more than 8 antenna ports,

는, CSI 자원 번호이고;

및

는 각각 집결된 CSI-RS 자원의 수 및 집결된 CSI-RS 자원 당 안테나 포트의 수를 나타낸다. 전술된 바와 같이, 12 포트 및 16-포트 NZP CSI-RS 설계 경우들에 대한

및

의 허용된 값은 표 2에 나와 있다.here,

is a CSI resource number;

and

denotes the number of aggregated CSI-RS resources and the number of antenna ports per aggregated CSI-RS resource, respectively. As described above, for 12-port and 16-port NZP CSI-RS design cases

and

Allowed values of is given in Table 2.

[Table 1]

Mapping from CSI reference signal configuration to (k', l') for general periodic prefix - taken from Table 6.10.5.2-1 of 3GPP TS 36.211.

. 일반 서브 프레임에 대한 구성들 0 내지 19는 프레임 구조 유형 1, 2 및 3에 대해 이용가능하다. 구성들 20 내지 31 및 특별 서브프레임에 대한 구성들은 프레임 구조 유형 2에 대해서만 이용가능하다.Notice :

. Configurations 0 to 19 for normal sub-frame are available for frame structure types 1, 2 and 3. Configurations 20 to 31 and configurations for special subframe are only available for frame structure type 2.

[Table 2]

Aggregation of CSI-RS resources - taken from Table 6.10.5-1 of 3GPP TS 36.211

9 shows a resource element grid in an exemplary NZP CSI-RS design for 12 ports with an OCC length of 4. Different 4-port NZP CSI-RS resources are indicated by letters A-J. For example, 4-port resources A, F and J may be aggregated to form a 12-port NZP CSI-RS resource. Length 4 OCC is applied within a CDM group, where the CDM group consists of 4 resource elements used to map the legacy 4-port CSI-RS. That is, resource elements labeled with the same character constitute one CDM group.

10 shows a resource element grid in an exemplary NZP CSI-RS design for 16 ports with an OCC length of 4. Different 8-port NZP CSI-RS resources are indicated by numbers (eg 0-4). Resource pairs containing 8-port resources are indicated by letters (eg, A-B). For example, resource pairs labeled A0 and B0 form one 8-port NZP CSI-RS resource. The resource pairs labeled A3 and B3 form another 8-port NZP CSI-RS resource. For example, 8-port NZP CSI-RS resources 0 and 3 may be aggregated, for example, to form a 16-port NZP CSI-RS resource. A and B are CDM groups in each 8-port resource. Within each CDM group, an OCC of length 4 is applied.

의, 안테나 포트 p에서의 기준 심볼로서 이용되는 복소값 변조 심볼들

로의 맵핑은 다음과 같이 정의된다 :For OCC length 4 (ie, when the upper layer parameter 'cdmType' is set to cdm4 - see 3GPP TS 36.331 for further details), the reference signal sequence of Equation 2

The complex-valued modulation symbols used as reference symbols at the antenna port p of

The mapping to is defined as:

here,

은 다운링크 전송 대역폭을 나타낸다;

은 집결된 CSI-RS 자원 당 안테나 포트의 수를 나타낸다; 인덱스 k' 및 l'는 (각각의 RB의 하단으로부터 시작하는) 서브캐리어 인덱스 및 (각각의 슬롯의 우측으로부터 시작하는) OFDM 심볼 인덱스를 나타낸다. 상이한 (k', l') 쌍들의 상이한 CSI-RS 자원 구성들로의 맵핑이 표 1에 나와 있다. 또한, 수학식 6의

는 표 3에 의해 주어진다.In Equations 6 and 7,

denotes the downlink transmission bandwidth;

denotes the number of antenna ports per aggregated CSI-RS resource; The indices k' and l' indicate the subcarrier index (starting from the bottom of each RB) and the OFDM symbol index (starting from the right side of each slot). The mapping of different (k', l') pairs to different CSI-RS resource configurations is shown in Table 1. Also, in Equation 6

is given by Table 3.

If the upper-layer parameter 'cdmType' is set to cdm4 for CSI-RS using more than 8 antenna ports, the antenna port number is as follows:

에 대해

Here, the CSI-RS resource number

About

[Table 3]

― 3GPP TS 36.211의 표 6.10.5.2-0으로부터 가져옴.sequence for CDM4

— taken from table 6.10.5.2-0 of 3GPP TS 36.211.

In the LTE Release 13 NZP CSI-RS design, the number of different 12-port and 16-port CSI-RS configurations in a subframe is 3 and 2, respectively. That is, in the case of 12 ports, three different CSI-RS configurations may be formed, where each configuration is formed by aggregating three legacy 4-port CSI-RS configurations. This consumes 36 CSI-RS resource elements out of 40 CSI-RS resource elements available for CSI-RS in the PRB. For 16 ports, two different CSI-RS configurations can be formed, where each configuration is formed by aggregating two legacy 8-port CSI-RS configurations. This consumes 32 CSI-RS resource elements out of 40 CSI-RS resource elements available for CSI-RS in the PRB.

In LTE, CSI-RS may be transmitted periodically in a predetermined subframe, called a CSI-RS subframe. In NR, CSI-RS may be transmitted on certain slots (ie, CSI-RS slots). The term CSI-RS subframe may be referred to as a CSI-RS slot. The CSI-RS subframe/slot configuration consists of a subframe/slot period and a subframe/slot offset. In LTE, the period may consist of 5, 10, 20, 40 and 80 ms.

The CSI-RS configuration consists of a CSI-RS resource configuration and a CSI-RS subframe configuration. The UE may be configured with up to three CSI-RS configurations for CSI feedback.

To improve CSI-RS channel estimation, the eNB may not transmit any signal in a given CSI-RS RE, referred to as zero-power CSI-RS or ZP CSI-RS. The CSI-RS used for CSI estimation is also referred to as non-zero power CSI-RS or NZP CSI-RS. The ZP CSI-RS RE of the first transmission (on the first cell, on the first beam, and/or for the first UE) of the second transmission (on the second cell, on the second beam, and/or the second When matching the NZP CSI-RS RE for UE), the first transmission does not interfere with the NZP CSI-RS of the second transmission. By avoiding interference in this way, CSI-RS channel estimation for cells, beams and/or UEs may be improved.

When a physical channel or signal is transmitted K times on separate orthogonal resources, it is referred to as the reuse factor K. The reuse coefficient of K cells for CSI-RS is that K non-overlapping (ie, not occupying the same RE if occupying the same subframe) CSI-RS resources are configured or reserved in each cell, and among K resources This means that one is used by each cell.

11 shows an example of a reuse factor K = 3 for CSI-RS. More specifically, FIG. 11 shows an example of a reuse factor K = 3 for CSI-RS, where three CSI-RS resources are configured in each cell but only one CSI-RS resource is NZP CSI-RS It is configured for RS and the other two resources are configured as ZP CSI-RS.

NZP CSI-RSs in different cells do not overlap. For example, if 21 of 40 REs available for CSI-RS in one subframe are used by one cell for NZP CSI-RS, the remaining 19 CSI-RS REs are 20-port in another cell It is not sufficient to configure the NZP CSI-RS. Therefore, only one cell can transmit more than 20 NZP CSI-RSs in one subframe without CSI-RS collision with CSI-RSs of other cells. Therefore, to achieve a reuse factor of K>1 in more than 20 ports, cells must transmit their CSI-RS in different subframes. As discussed below, Rel-13 UEs may be generally configured to receive ZP CSI-RS in only one of the T _CSI-RS subframes.

Only CSI-RS REs for 4 antenna ports can be assigned to ZP CSI-RS. The ZP CSI-RS subframe configuration is associated with the ZP CSI-RS. This may be the same as or different from the NZP CSI-RS configuration.

The subframe configuration period T CSI_RS and subframe offset _{ΔCSI - RS} for the generation of the _CSI reference signal are listed in Table _6.10.5.3-1 of 3GPP TS 36.211 (shown in Table 4 below). The parameter I _{CSI - RS} of Table 4 may be configured separately for the CSI reference signal in which the UE assumes non-zero and zero transmit power.

[Table 4]

CSI reference signal subframe configuration (taken from Table 6.10.5.3-1 of 3GPP TS 36.211)

In general, a full-dimensional MIMO (FD-MIMO) UE (UE configured for class A or class B CSI reporting) may be configured with only one ZP CSI-RS configuration. A UE supporting discovery signal reception or reception using two subframe sets may support more than one ZP CSI-RS configuration. An FD-MIMO UE is not required to support these features.

Since the FD-MIMO UE supports only a maximum of 16 CSI-RS ports in Rel-13, as described above, two sets of 16 ports fit in one subframe, so NZP CSI using ZP CSI-RS A reuse factor of up to 2 can be supported while protecting -RS. However, since Rel-14 can include up to 32 ports, and only one ZP CSI-RS can be configured for certain FD-MIMO UEs in Rel-13, ZP CSI in different subframes Rel-13 mechanism to protect more than one NZP CSI-RS with -RS is not available. Thus, reuse pattern >2 is not possible for these UEs with 32 ports.

TM10 includes a concept called CSI process (see 3GPP TS 36.213). The CSI process is associated with an NZP CSI-RS resource and a CSI Interference Measurement (CSI-IM) resource. The CSI-IM resource is defined by the ZP CSI-RS resource and the ZP CSI-RS subframe configuration. A UE may be configured with up to three CSI-RS processes. Multiple CSI processes are used to support coordinated multi-point (COMP) transmission in which the UE measures the CSI associated with each transmission point (TP) and feeds it back to the eNB. Based on the received CSIs, the eNB may decide to send data from one of the TPs to the UE.

In Rel-13, the CSI-IM is always associated with the NZP CSI-RS resource in a one-to-one manner so that the number of CSI-IMs is equal to the number of NZP CSI-RS resources. Therefore, although the CSI-IM is configured from ZP CSI-RS resources, it is not suitable for preventing interference to other NZP CSI-RSs, so it is not useful for increasing the CSI-RS reuse factor.

Measurement constraints are included in LTE Release 13 for TM9 and TM10. CSI measurement may be limited to a CSI-RS resource or a CSI-IM resource in one subframe.

For the UE and CSI process of TM9 or TM10, the UE is configured with the parameter CSI-Reporting-Type by higher layers, the CSI-Reporting-Type is set to 'Class B', and the parameter channelMeasRestriction is set by the upper layers If configured, the UE determines, within the configured CSI-RS resource associated with the CSI process, the channel measurement for calculating the CQI value reported in uplink subframe n and corresponding to the CSI process, the most recent, not later than the CSI reference resource. It should be derived based only on the non-zero power CSI-RS of .

For the UE and CSI process of TM10, when the parameters CSI-Reporting-Type and interferenceMeasRestriction are configured by higher layers, the UE is reported in uplink subframe n and corresponding to the CSI process to calculate the CQI value. Interference measurements should be derived based only on the most recent configured CSI-IM resource associated with the CSI process, not later than the CSI reference resource.

Channel measurement constraint for one CSI-RS subframe is required in class B, where precoding for CSI-RS in different CSI-RS subframes may be different.

In LTE Rel-14, up to 32 antenna ports can be supported in the downlink. However, up to 40 CSI-RS REs per PRB in a CSI-RS subframe are available. Therefore, only one 32-port CSI-RS configuration per CSI-RS subframe can be supported. A mechanism for reducing the CSI-RS overhead and allowing a larger number of CSI-RS configurations using 32 ports is described in 3GPP TSG-RAN R1-163079, "CSI-RS Design for Class A eFD- MIMO" is being discussed. Measurement restriction (MR) in the frequency domain described in R1-163079 is one technique that can achieve these goals.

Although the general concept of MR in the frequency domain is described in R1-163079, some details of this technique are still missing. For example, one problem is that when the measurement constraint is configured, how the UE interprets the resource element-to-port mapping is not clearly defined.

As shown in Table 4, the ZP CSI-RS for the serving cell may be configured with only a single CSI-RS-SubframeConfig parameter when the UE supports only one ZP CSI-RS configuration. This means that ZP CSI-RS can only occur in one given subframe configuration. However, as the number of CSI-RS ports available in LTE Release 14 increases, achieving a reuse factor greater than 1 for a CSI-RS within a single subframe is difficult for a large number of CSI, such as 32 CSI-RS ports. -Not possible for RS port.

Embodiments described herein include resource element (RE) to port mapping for measurement constraint (MR) in the frequency domain (FD). Certain embodiments include a port mapping scheme for the case where the eNB semi-statically configures a user equipment (UE) to measure all ports on a subset of physical resource blocks (PRBs). Some embodiments include various alternatives to how MR sets may be signaled.

A particular embodiment is a port mapping for the case where the UE is semi-statically configured to measure a subset of CSI-RS ports on one set of PRBs and channels on another set of antenna ports and on a different set of PRBs. including method. Various alternatives to a CSI-RS resource set comprising a subset of MR sets and ports are described. Certain embodiments describe how RE to port mapping is performed using RRC configured MR_set and/or CSI-RS resource set parameters in a configurable manner.

Some embodiments include multiple ZP CSI-RS subframe configurations. For example, certain embodiments include configuring a plurality of ZP CSI-RS subframe configurations to enable a higher reuse factor.

According to some embodiments, a method for use in a network node transmitting a channel state information reference signal (CSI-RS) includes a subset of physical resource blocks (PRBs) that a wireless device should use to measure the CSI-RS. sending an indication of to the wireless device. Each CSI-RS is associated with an antenna port. The subset of PRBs includes a subset of system bandwidth. The method further includes transmitting the CSI-RS on the indicated subset of PRBs.

The method may further include, prior to sending the indication, obtaining, by the network node, an indication of a subset of physical resource blocks (PRBs) that the wireless device should use to measure the CSI-RS. have.

In a particular embodiment, the network node transmits CSI-RS on a total number of antenna ports (eg, greater than 16), and each PRB in the subset of PRBs is a CSI-RS mapping for the total number of antenna ports. includes

In a particular embodiment, the subset of PRBs that the wireless device should use to measure the CSI-RS includes even-numbered PRBs or odd-numbered PRBs. An indication of the subset of PRBs that the wireless device should use to measure the CSI-RS may include a density value and a comb offset.

를 포함한다. 제2 콤 오프셋은, 무선 디바이스가 CSI-RS를 측정하기 위해 세트 m2에 의해 식별되는 PRB들이 아니라, 세트 m2 내의 PRB들을 이용해야 한다는 것을 나타내고, 여기서, 세트 m2는

을 포함한다.For example, the density value may include a density of 1/2. The first comb offset indicates that the wireless device should use the PRBs in the set m1, not the PRBs identified by the set m1, to measure the CSI-RS, where the set m1 is

includes The second comb offset indicates that the wireless device should use PRBs in set m2, not the PRBs identified by set m2, to measure the CSI-RS, where set m2 is

includes

을 포함한다. 제2 콤 오프셋은, 무선 디바이스가 CSI-RS를 측정하기 위해 세트 m2에 의해 식별되는 PRB들이 아니라, 세트 m2 내의 PRB들을 이용해야 한다는 것을 나타내고, 여기서, 세트 m2는

를 포함한다. 제3 콤 오프셋은, 무선 디바이스가 CSI-RS를 측정하기 위해 세트 m3에 의해 식별되는 PRB들이 아니라, 세트 m3 내의 PRB들을 이용해야 한다는 것을 나타내고, 여기서, 세트 m3은

을 포함한다.As another example, the density value may include a density of 1/3. The first comb offset indicates that the wireless device should use the PRBs in the set m1, not the PRBs identified by the set m1, to measure the CSI-RS, where the set m1 is

includes The second comb offset indicates that the wireless device should use PRBs in set m2, not the PRBs identified by set m2, to measure the CSI-RS, where set m2 is

includes The third comb offset indicates that the wireless device should use PRBs in set m3, not the PRBs identified by set m3, to measure the CSI-RS, where set m3 is

includes

An indication of the subset of PRBs that the wireless device should use to measure the CSI-RS port may include an index value k. The index value k refers to one of a plurality of indications stored in the wireless device.

In a particular embodiment, the indication of the subset of PRBs that the wireless device should use to measure the CSI-RS port further increases the number of consecutive CSI-RS subframes/slots over which the wireless device should measure the CSI-RS. include

The method may further include receiving, from the wireless device, channel state information (CSI) determined based on a measurement of one or more of the transmitted CSI-RSs.

According to some embodiments, a method for use in a wireless device that receives a CSI-RS includes receiving an indication of a subset of PRBs that the wireless device should use to measure the CSI-RS. Each CSI-RS is associated with an antenna port. The subset of PRBs includes a subset of system bandwidth. The method further includes receiving the CSI-RS on the indicated subset of PRBs. The method may further include determining CSI based on the received CSI-RS and transmitting the CSI to the network node.

In a particular embodiment, the network node transmits a CSI-RS on a total number of antenna ports (eg, greater than 16), and each PRB in the subset of PRBs is a CSI-RS for the total number of antenna ports. Includes mapping.

In a particular embodiment, the subset of PRBs that the wireless device should use to measure CSI-RS includes even-numbered PRBs or odd-numbered PRBs. An indication of the subset of PRBs that the wireless device should use to measure the CSI-RS port may include a density value and a comb offset.

를 포함한다. 제2 콤 오프셋은, 무선 디바이스가 CSI-RS를 측정하기 위해 세트 m2에 의해 식별되는 PRB들이 아니라, 세트 m2 내의 PRB들을 이용해야 한다는 것을 나타내고, 여기서, 세트 m2는

을 포함한다.For example, the density value may include a density of 1/2. The first comb offset indicates that the wireless device should use the PRBs in the set m1, not the PRBs identified by the set m1, to measure the CSI-RS, where the set m1 is

includes The second comb offset indicates that the wireless device should use PRBs in set m2, not the PRBs identified by set m2, to measure the CSI-RS, where set m2 is

includes

을 포함한다. 제2 콤 오프셋은, 무선 디바이스가 CSI-RS를 측정하기 위해 세트 m2에 의해 식별되는 PRB들이 아니라, 세트 m2 내의 PRB들을 이용해야 한다는 것을 나타내고, 여기서, 세트 m2는

를 포함한다. 제3 콤 오프셋은, 무선 디바이스가 CSI-RS를 측정하기 위해 세트 m3에 의해 식별되는 PRB들이 아니라, 세트 m3 내의 PRB들을 이용해야 한다는 것을 나타내고, 여기서, 세트 m3은

을 포함한다.As another example, the density value may include a density of 1/3. The first comb offset indicates that the wireless device should use the PRBs in the set m1, not the PRBs identified by the set m1, to measure the CSI-RS, where the set m1 is

includes The second comb offset indicates that the wireless device should use PRBs in set m2, not the PRBs identified by set m2, to measure the CSI-RS, where set m2 is

includes The third comb offset indicates that the wireless device should use PRBs in set m3, not the PRBs identified by set m3, to measure the CSI-RS, where set m3 is

includes

An indication of the subset of PRBs that the wireless device should use to measure the CSI-RS port may include an index value k. The index value k refers to one of a plurality of indications stored in the wireless device.

In a particular embodiment, the indication of the subset of PRBs that the wireless device should use to measure the CSI-RS port further includes a number of consecutive CSI-RS subframes/slots for which the wireless device should measure the CSI-RS. include

In a particular embodiment, the method further comprises determining CSI based on the CSI-RS received over a number of consecutive CSI-RS subframes/slots.

In accordance with some embodiments, a network node operable to transmit a CSI-RS includes processing circuitry. The processing circuitry is operable to send to the wireless device an indication of a subset of PRBs that the wireless device should use to measure the CSI-RS. Each CSI-RS is associated with an antenna port. The subset of PRBs includes a subset of system bandwidth. The processing circuitry is also operable to transmit the CSI-RS on the indicated subset of PRBs.

The processing circuitry is also operable to obtain, prior to transmitting the indication, an indication of a subset of physical resource blocks (PRBs) that the wireless device should use to measure the CSI-RS.

In accordance with some embodiments, a wireless device operable to receive a CSI-RS includes processing circuitry. The processing circuitry is operable to receive an indication of the subset of PRBs that the wireless device should use to measure the CSI-RS. Each CSI-RS is associated with an antenna port. The subset of PRBs includes a subset of system bandwidth. The processing circuitry is also operable to receive the CSI-RS on the indicated subset of PRBs.

According to some embodiments, a network node operable to transmit the CSI-RS comprises a transmitting module. The network node may further include an acquiring module. The obtaining module is operable to obtain an indication of the subset of PRBs that the wireless device should use to measure the CSI-RS. The transmitting module is configured to: send to the wireless device an indication of the subset of PRBs that the wireless device should use to measure the CSI-RS; operable to transmit CSI-RS on the indicated subset of PRBs.

In accordance with some embodiments, a wireless device operable to receive a CSI-RS includes a receiving module. The receiving module is configured to receive an indication of the subset of PRBs that the wireless device should use to measure the CSI-RS; operable to receive CSI-RS on the indicated subset of PRBs.

Also disclosed is a computer program product. The computer program product, when executed by the processor, comprises: sending to the wireless device an indication of a subset of PRBs that the wireless device should use to measure CSI-RS; and instructions stored on a non-transitory computer-readable medium for performing the operation of transmitting the CSI-RS on the indicated subset of PRBs. The computer program product further includes instructions stored on a non-transitory computer-readable medium that, when executed by a processor, perform the operation of obtaining an indication of a subset of PRBs that the wireless device should use to measure CSI-RS. can do.

Another computer program product includes: receiving an indication of a subset of PRBs that a wireless device should use to measure CSI-RS when executed by a processor; and instructions stored on a non-transitory computer-readable medium for performing the operation of receiving a CSI-RS on the indicated subset of PRBs.

Certain embodiments may exhibit some of the following technical advantages. As an example, certain embodiments may enable measurement constraint techniques in the frequency domain by using an efficient and flexible RE-to-port mapping scheme. As another example, certain embodiments may enable different CSI-RS ports to have different CSI-RS densities in the frequency domain. As yet another example, certain embodiments may enable a higher reuse factor for CSI-RS transmission using a greater number of ports (eg, 32 ports).

Other technical advantages will become readily apparent to those skilled in the art from the following drawings, detailed description and claims.

For a more complete understanding of embodiments and their features and advantages, reference is now made to the following description taken in conjunction with the accompanying drawings.
1 shows an exemplary downlink radio subframe;
2 shows an exemplary radio frame;
3 shows an exemplary downlink subframe;
4 is a block diagram illustrating a logical structure of a precoded spatial multiplexing mode in LTE;
5 shows a resource element grid with resource block pairs indicating potential locations for CSI-RS for 2, 4, and 8 antenna ports;
6A and 6B show a resource element grid with resource block pairs indicating potential locations for CSI-RS for 12 and 16 antenna ports, respectively;
7 shows a resource element grid in an exemplary NZP CSI-RS design for 12 ports with an OCC length of 2;
8 shows a resource element grid in an exemplary NZP CSI-RS design for 16 ports with an OCC length of 2;
9 shows a resource element grid in an exemplary NZP CSI-RS design for 12 ports with an OCC length of 4;
10 shows a resource element grid in an exemplary NZP CSI-RS design for 16 ports with an OCC length of 4;
11 shows an example of a reuse factor K = 3 for CSI-RS;
12 is a block diagram illustrating an example wireless network in accordance with some embodiments;
13 shows an example of CSI-RS transmission in which all ports are transmitted on one constrained set of PRBs, according to certain embodiments;
14 is an example of CSI-RS transmission in which one set of ports are transmitted on one constrained set of PRBs and another set of ports are transmitted on another constrained set of PRBs, according to certain embodiments; represents;
15 illustrates an example of CSI-RS transmission in which one set of ports are transmitted on all PRBs and another set of ports are transmitted on a constrained set of PRBs, according to certain embodiments;
16 shows an example of configuring a plurality of ZP CSI-RS subframes according to an embodiment;
17 is a flow diagram illustrating an exemplary method in a network node for transmitting channel state information reference signals (CSI-RSs), in accordance with some embodiments;
18 is a flow diagram illustrating an example method at a wireless device for receiving channel state information reference signals (CSI-RS), in accordance with some embodiments;
19A is a block diagram illustrating an exemplary embodiment of a wireless device;
19B is a block diagram illustrating example components of a wireless device;
20A is a block diagram illustrating an exemplary embodiment of a network node;
20B is a block diagram illustrating example components of a network node;
21A and 21B show examples of overhead for a TDM scheme;

The Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) uses a non-zero power channel state information reference symbol (NZP CSI-RS) as a flexible means of configuring channel state information (CSI) feedback measurements. By measuring with respect to the NZP CSI-RS, the user equipment (UE) can estimate the effective channels traversed by the NZP CSI-RS, including radio propagation channels and antenna gains.

In LTE Rel-14, up to 32 antenna ports can be supported in the downlink. However, a maximum of 40 CSI-RS resource elements (REs) per physical resource block (PRB) in a CSI-RS subframe are available. Therefore, only one 32-port CSI-RS configuration can be supported per CSI-RS subframe. Certain embodiments may avoid the above-mentioned problems, reduce CSI-RS overhead, and facilitate configuration of a larger number of CSI-RSs with 32 ports.

In certain embodiments, a method for establishing resource element-to-port mapping for measurement constraints in the frequency domain is described. According to one exemplary embodiment, a port mapping scheme is described for the case where the eNB semi-statically configures the UE to measure all ports on a subset of PRBs. Various alternatives to how measurement constraint sets are signaled are described. According to another example, port mapping for the case where the UE is semi-statically configured to measure a subset of CSI-RS ports on one set of PRBs and channels on another subset of antenna ports on a different set of PRBs. method is proposed. Various alternatives are described for how a particular antenna port is assigned to a set of measurement constraints and/or a set of CSI-RS resources. In certain embodiments, a solution is described for how RE to port mapping may be performed using RRC configured MR_set and/or CSI-RS resource set parameters in a configurable manner.

(여기서,

)로 식별될 수 있고, 제2 PRB는

로 식별될 수 있으며, k는 및 음이 아닌 정수이다. 일부 경우에, 제1 PRB는 세트 M 내에 있는 인덱스

으로 식별될 수 있고, 제2 PRB는 세트 M 내에 있지 않은 인덱스

로 식별될 수 있으며, 여기서, 네트워크는 세트 M을 UE에 시그널링한다.In certain embodiments, the network can determine whether the UE can assume that a first PRB in a slot of a subframe includes a CSI-RS port transmission and a second PRB in a slot of a subframe does not include a CSI-RS port transmission. indicate to the UE, where the CSI-RS port is identified by a non-negative integer. In some cases, the first PRB is an index

(here,

) can be identified, and the second PRB is

can be identified, and k is a non-negative integer. In some cases, the first PRB is an index in the set M

can be identified as, the second PRB is an index that is not in the set M

, where the network signals the set M to the UE.

Accordingly, the PRBs included in the PRBs of the various alternative subsets discussed herein may be identified by their respective PRB indexes, and a set of such PRB indices may be used to define a subset of PRBs. A subset of PRBs is a smaller set compared to a set of PRBs spanning the system bandwidth of a wireless network, eg, an LTE system bandwidth or an NR system bandwidth. The subset of PRBs may include PRBs that are also included in the PRB set across the system bandwidth. As used herein, PRBs may sometimes be referred to as being included in a set of indexes (such as index set m1, m2 or m3), and strictly speaking, a PRB index identifying a PRB is included in the index set. This expression is used for simplicity and is not intended to be limiting.

In certain embodiments, methods for establishing a plurality of ZP CSI-RS subframe configurations are described. According to one exemplary embodiment, a solution of configuring a plurality of ZP CSI-RS subframe configurations to enable a higher reuse factor is described. As described in more detail below, in some cases, a method of avoiding interference to NZP CSI-RS that is not intended for a UE is that the network comprises: one NZP CSI-RS resource, and first and second sub configuring the UE with first and second zero power (ZP) CSI-RS resources occurring in a frame, wherein at least one of the first and second ZP CSI-RS resources is one of the P subframes. With periodicity, the first and second subframes are distinguished within the period P. In some cases, a method of avoiding interference for NZP CSI-RSs that are not intended for a UE comprises: configuring a UE such that a network receives one NZP CSI-RS and first and second zero power CSI-RSs; includes A first zero-power CSI-RS occurs in a first subframe and a second zero-power CSI-RS occurs in a second subframe.

The various embodiments described herein may have one or more technical advantages. As an example, certain embodiments may enable measurement constraint techniques in the frequency domain by proposing an efficient/flexible RE-to-port mapping scheme. As another example, certain embodiments may enable a higher reuse factor for CSI-RS transmission using a larger number of ports (eg, 32 ports).

The following description discloses numerous specific details. It should be understood, however, that embodiments may be practiced without these specific details. In other instances, well-known circuits, structures, and techniques have not been shown in detail in order not to obscure the understanding of this description. Those skilled in the art will be able to implement appropriate functions without undue experimentation through the included description.

References in the specification to “one embodiment,” “an embodiment,” “an exemplary embodiment,” or the like, indicate that although the described embodiment may include a particular feature, structure, or characteristic, all embodiments necessarily include that particular feature, It indicates that it does not include structures, or features. Moreover, such phrases are not necessarily referring to the same embodiment. Also, when a particular feature, structure, or characteristic is described in connection with one embodiment, it is within the skill of the art to implement that feature, structure, or characteristic in connection with other embodiments, whether explicitly described or not. It can be said that it is within the knowledge of a person skilled in the art.

In this specification, the terms of 3GPP LTE are used to describe specific embodiments, but the embodiments are not limited to the aforementioned systems. Other wireless systems, including New radio (NR), Wideband Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra-Mobile Broadband (UMB) and Global System for Mobile Communication (GSM), etc. One may benefit from the embodiments described herein.

Terms such as eNodeB and UE should be considered non-limiting and do not imply a specific hierarchical relationship between the two. In NR, a node corresponding to an eNodeB is called a gNodeB. In general, an “eNodeB” may be considered a first device and an “UE” may be considered a second device. The two devices communicate with each other over a radio channel. While certain embodiments describe wireless transmission in the downlink, other embodiments are equally applicable in the uplink.

Certain embodiments are described with reference to FIGS. 12-20B of the drawings, in which like reference numerals are used for like and corresponding parts of the various drawings. Although LTE is used throughout this specification as an example cellular system, the ideas presented herein are applicable to other wireless communication systems as well.

12 is a block diagram illustrating an example wireless network in accordance with certain embodiments. The wireless network 100 includes one or more wireless devices 110 (such as a mobile phone, smart phone, laptop computer, tablet computer, MTC device, or any other device capable of providing wireless communication) and (a base station or eNodeB) etc.) includes a plurality of network nodes 120 . Wireless device 110 may also be referred to as a UE. Network node 120 provides a coverage area 115 (also referred to as cell 115 ).

In general, a wireless device 110 that is within coverage of a network node 120 (eg, within a cell 115 serviced by the network node 120 ) can transmit and receive a wireless signal 130 by sending and receiving a wireless signal 130 . It communicates with the network node 120 . For example, wireless device 110 and network node 120 may carry wireless signals 130 including voice traffic, data traffic, and/or control signals. A network node 120 that delivers voice traffic, data traffic, and/or control signals to the wireless device 110 may be referred to as a serving network node 120 for the wireless device 110 . Communication between the wireless device 110 and the network node 120 may be referred to as cellular communication. The wireless signal 130 may include both a downlink transmission (from the network node 120 to the wireless device 110 ) and an uplink transmission (from the wireless device 110 to the network node 120 ).

The network node 120 and the wireless device 110 may convey the wireless signal 130 according to a radio frame and subframe structure similar to those described with respect to FIGS. 1-3 . Other embodiments may include any suitable radio frame structure. For example, in NR, the duration of a time symbol (such as an OFDM symbol) may vary depending on the numerology used, and thus a subframe may not always contain the same number of symbols. Instead, the concept of “slot” can be used, and a slot usually occupies 14 symbols, or sometimes 7 symbols, and thus corresponds to an LTE subframe.

Each network node 120 may have a single transmitter 140 or multiple transmitters 140 for transmitting a signal 130 to the wireless device 110 . In some embodiments, network node 120 may comprise a multiple-input multiple-output (MIMO) system. Similarly, each wireless device 110 may have a single receiver or multiple receivers for receiving the signal 130 from the network node 120 or other wireless device 110 . A plurality of transmitters of the network node 120 may be associated with a logical antenna port.

The radio signal 130 may include a reference signal such as a CSI-RS reference signal 135 . In certain embodiments, the radio signal 130 may include more than 16 CSI-RSs 135 in a subframe. Each CSI-RS 135 may be associated with an antenna port.

In a particular embodiment, a network node, such as network node 120 , transmits multiple CSI-RSs 135 to one or more wireless devices, such as wireless device 110 . In a particular embodiment, the number of CSI-RS ports, ie, ports through which CSI-RS 135 is transmitted, is greater than 16. For example, the number of CSI-RS ports may be 32.

In a particular embodiment, network node 120 may obtain an indication of a subset of PRBs that wireless device 110 should use to measure CSI-RS. The network node 120 may send the wireless device 110 an indication of the subset of PRBs that the wireless device 110 should use to measure the CSI-RS.

In a particular embodiment, the network node 120 configures the network node 120 as an indication of PRB indices (eg, odd or even numbered PRB), as a density value and as a comb offset (eg, density 1 with two comb offsets). /2, density 1/3 with 3 comb offset, etc.), or as an index value indicating an indication or pattern of PRBs known to wireless device 110 (eg, index k, where k is wireless device 110 ). ), which identifies a specific PRB pattern known to ), may send an indication of the PRBs to the wireless device 110 .

In a particular embodiment, the network node 120 may send an indication to the wireless device 110 of the number of consecutive subframes that the wireless device should use to measure the CSI-RS. In a particular embodiment, the network node 120 may receive, from the wireless device 110 , channel state information (CSI) based on one or more of the transmitted CSI-RS 135 .

According to some embodiments, a wireless device, such as wireless device 110 , receives an indication of a subset of PRBs that wireless device 110 should use to measure CSI-RS. The wireless device 110 receives the CSI-RS on the indicated subset of PRBs. The wireless device 110 may determine channel state information (CSI) based on the received CSI-RS (ie, measure the received CSI-RS to estimate an effective channel), and set the CSI to the network node 120 ) can be sent to

In the wireless network 100 , each network node 120 includes long term evolution (LTE), LTE-Advanced, Universal Mobile Telecommunications System (UMTS), High Speed Packet Access (HSPA), GSM, cdma2000, NR, WiMax , WiFi (Wireless Fidelity), and/or other suitable radio access technology may be used. Wireless network 100 may include any suitable combination of one or more radio access technologies. For purposes of illustration, various embodiments may be described within the context of a given radio access technology. However, the scope of the present disclosure is not limited to the examples, and other embodiments may use different radio access technologies.

As noted above, embodiments of a wireless network may include one or more wireless devices, and one or more different types of network nodes or radio network nodes capable of communicating with the wireless devices. The network may also include any additional elements suitable to support communication between wireless devices, or between a wireless device and another communication device (such as a landline phone). A wireless device may include any suitable combination of hardware and/or software. For example, in certain embodiments, a wireless device, such as wireless device 110 , may include the components described with respect to FIG. 19A below. Similarly, a network node may comprise any suitable combination of hardware and/or software. For example, in a particular embodiment, a network node, such as network node 120 , may include the components described with respect to FIG. 20A below.

According to a first group of exemplary embodiments, the eNB configures the UE semi-statically to measure all ports on a subset of PRBs. The NZP CSI-RS corresponding to all ports is transmitted only on the configured PRB. The eNB radio resource control (RRC) configures the UE with a frequency domain measurement constraint parameter MR_Set including all PRBs for which the UE should measure the CSI-RS port. An example of this embodiment is shown in FIG. 13 .

개를 포함한다. PRB들(16a)은 어떠한 NZP CSI-RS 전송도 수반하지 않는 PRB들을 나타낸다. PRB들(16b)은 NZP CSI-RS 전송을 수반하는 CSI 측정을 위한 PRB들을 나타낸다.13 shows an example of CSI-RS transmission in which all ports are transmitted on one constrained set of PRBs, according to certain embodiments. In the illustrated example, the system bandwidth, such as the system bandwidth of the network 100 described above, is equal to that of the PRB 16 .

includes dogs. PRBs 16a represent PRBs that do not involve any NZP CSI-RS transmission. PRBs 16b represent PRBs for CSI measurement accompanying NZP CSI-RS transmission.

를 포함한다(즉, MR_Set = {0, 2, 4, ...

}). 수학식 4와 수학식 7에서 RE 대 포트 맵핑 공식의 PRB 인덱스 m은 다음과 같이 수정된다:Parameter MR_Set, PRBs

contains (i.e., MR_Set = {0, 2, 4, ...

}). In Equations 4 and 7, the PRB index m of the RE-to-port mapping formula is modified as follows:

In other words, Equation 9 shows that to a UE, such as wireless device 110 , the UE sends NZP CSI-RSs corresponding to all NZP CSI-RS ports in the PRBs indicated by the set MR_Set, but in other PRBs Indicates that it can be assumed that it is not necessarily transmitted. Accordingly, the UE must measure the channel corresponding to the ports in the indicated PRBs. Because the NZP CSI-RS can be sent to the UE in a configurable subset of PRBs, the overhead associated with the CSI-RS can advantageously be reduced in a configurable manner for different deployment scenarios and load conditions.

의 비트맵으로서 시그널링될 수 있고, 여기서, m번째 비트는, NZP CSI-RS가 m번째 PRB 상에서 전송되는지의 여부를 나타낸다. 소정 실시예에서, UE는, NZP CSI-RS가 전송될 때마다 MR_Set의 값을 이용하도록 구성된다.In some embodiments, the RRC parameter MR_Set is the length

may be signaled as a bitmap of , where the m-th bit indicates whether the NZP CSI-RS is transmitted on the m-th PRB. In certain embodiments, the UE is configured to use the value of MR_Set whenever an NZP CSI-RS is transmitted.

를 포함한다.In some embodiments, the set of PRB indices is an integer that identifies which PRBs contain at least one NZP CSI-RS. In a particular embodiment, each of the integers is a physical resource block number, as defined in section 6.2.3 of 3GPP TS 36.211;

includes

In the example shown in FIG. 13 , PRBs for CSI measurement include even-numbered PRBs, and PRBs not accompanied by any NZP CSI-RS transmission include odd-numbered PRBs. In some embodiments, the RRC parameter MR_Set may be signaled as a value indicating an odd or even number. The same pattern can be represented by a combination of density and comb offset. For example, the illustrated example includes a density of 1/2 (ie, half of the PRBs contain CSI-RS and the other half do not). The first comb offset may indicate that an even-numbered PRB includes a CS-RS and an odd-numbered PRB does not include a CS-RS. The second comb offset may indicate that odd-numbered PRBs include CS-RSs and even-numbered PRBs do not include CS-RSs. The illustrated example is only one example. Other embodiments may use other densities and comb offsets (eg, 1/3 density with 3 comb offsets).

In some embodiments, the UE is configured to cover the entire band or a part thereof by examining successive CSI-RS subframes (ie, subframes including CSI-RS) to which a different MR_Set is applied over the successive subframes. A channel estimate can be built across This can be particularly useful for UEs with low mobility. The eNB may signal what will be successive subframes for which the UE should measure the CSI-RS.

In some embodiments, a fixed number of measurement constraint (MR) patterns in the frequency domain may be predefined. For example, the first measurement constraint pattern in the frequency domain may include an NZP CSI-RS in every second PRB, and the second measurement constraint pattern in the frequency domain may include an NZP CSI-RS in every fourth PRB. And, the third measurement constraint pattern in the frequency domain may include the NZP CSI-RS in all PRBs. This can be generalized to K different predefined measurement constraint patterns in the frequency domain. The eNB may semi-statically configure the UE to use one of K predefined measurement constraint patterns in the frequency domain. For example, if the kth measurement constraint pattern in the frequency domain is to be configured for a particular UE, the eNB may semi-statically signal the integer parameter along with the value k to the UE.

According to a second group of exemplary groups, the UE is semi-statically configured to measure channels on a subset of CSI-RS ports on one set of PRBs and another subset of antenna ports on a different set of PRBs. The eNB RRC configures the UE with a first set of frequency domain measurement constraint parameters MR_Set1 applied to the first set of ports in the CSI-RS resource set CSI-RS_Resource_Set1. Similarly, the eNB RRC configures the UE with a second set of frequency domain measurement constraint parameters MR_Set2 applied to the second set of ports in the CSI-RS resource set CSI-RS_Resource_Set2.

Resources indicated in CSI-RS_Resource_Set1 and CSI-RS_Resource_Set2 are selected from among the resources in the parameter 'nzp-resourceConfigList' indicated by higher layers (refer to 3GPP TS 36.331). Each of the RRC parameters MR_Set1 and MR_Set2 includes a list of PRBs in which the NZP CSI-RS corresponding to the respective sets is transmitted. An example of this embodiment with 32 CSI-RS ports is shown in FIG. 14 .

14 is an example of CSI-RS transmission in which one set of ports are transmitted on one constrained set of PRBs and another set of ports are transmitted on another constrained set of PRBs, according to certain embodiments; indicates The resource element grid shown in FIG. 14 includes a part of a subframe 10 having two PRBs 16 .

CSI-RS ports 15 to 30 are transmitted in even-numbered PRBs 16 , and CSI-RS ports 31 to 46 are transmitted in odd-numbered PRBs 16 . The MR_Set1 parameter corresponding to ports 15 to 30 includes PRBs 0, 2, 4, 6, ... (ie, MR_Set1 = {0, 2, 4, 6, ...}); The MR_Set2 parameter corresponding to ports 31 to 46 includes PRBs 1, 3, 5, 7, ... (ie, MR_Set2 = {1, 3, 5, 7, ...}). In Equations 5 and 8, the quantity i'' related to the number of legacy CSI resources i' is defined as follows:

이고, 여기서,

은 제1 CSI-RS_Resource_Set1에 대응하고,

은 제2 CSI-RS_Resource_Set2에 대응한다. 도 14의 예에서, 슬롯 0의 OFDM 심볼 5 및 6 내의 CSI-RS RE는 8-포트 레거시 자원(레거시 자원 번호 i'=0에 대응함)에 속하고 슬롯 1의 OFDM 심볼 5 및 6의 CSI-RS RE는 또 다른 8-포트 레거시 자원(레거시 자원 번호 i'=1에 대응)에 속한다.In Equation 10,

and where,

corresponds to the first CSI-RS_Resource_Set1,

corresponds to the second CSI-RS_Resource_Set2. In the example of FIG. 14, CSI-RS REs in OFDM symbols 5 and 6 of slot 0 belong to an 8-port legacy resource (corresponding to legacy resource number i'=0) and CSI-RS REs of OFDM symbols 5 and 6 of slot 1 RS RE belongs to another 8-port legacy resource (corresponding to legacy resource number i'=1).

)의 경우, 새로운 CSI 기준 번호는

이고; CSI-RS_Resource_Set2(여기서

)의 경우, 새로운 CSI 기준 번호는

이다. 따라서, 수학식 10을 이용하여, 도 14의 예에서 레거시 CSI 자원 번호

를 갖는 2개의 레거시 8-포트 자원은 새로운 CSI 기준 번호

를 갖는 4개의 새로운 8-포트 자원으로 분할된다.The quantity i'' may be used as a new CSI resource number for the resources of CSI-RS_Resource_Set1 and CSI-RS_Resource_Set2. CSI-RS_Resource_Set1 (where

), the new CSI reference number is

ego; CSI-RS_Resource_Set2 (where

), the new CSI reference number is

to be. Therefore, using Equation 10, the legacy CSI resource number in the example of FIG. 14

The two legacy 8-port resources with

is divided into four new 8-port resources with

If the upper layer parameter 'cdmType' is set to cdm2 for CSI-RS using more than 8 antenna ports, port numbering may be assigned using a new CSI reference number as follows:

If the upper layer parameter 'cdmType' is set to cdm4 for CSI-RS using more than 8 antenna ports, an antenna port number may be assigned using a new CSI reference number as follows:

에 대응한다; CSI-RS 포트들 23 내지 30을 갖는 새로운 자원은

에 대응한다; CSI-RS 포트 31 내지 3을 갖는 새로운 자원은

에 대응한다; CSI-RS 포트 39 내지 46을 갖는 새로운 자원은

에 대응한다. 전술된 바와 같이, MR_Set1은 (

에 대응하는) CSI-RS_Resource_Set1에 적용되고, MR_Set2는 (

에 대응하는) CSI-RS_Resource_Set2에 적용된다.For example, in the example of FIG. 14 , a new resource with CSI-RS ports 15 to 22 is

corresponds to; A new resource with CSI-RS ports 23 to 30 is

corresponds to; New resources with CSI-RS ports 31 to 3 are

corresponds to; New resources with CSI-RS ports 39 to 46 are

respond to As described above, MR_Set1 is (

is applied to CSI-RS_Resource_Set1 (corresponding to

corresponding to ) is applied to CSI-RS_Resource_Set2.

To define the RE-to-port mapping formula for this embodiment, the PRB index m in Equations 4 and 7 is modified as follows:

Here, the new CSI-RS resource number i" is defined as in Equation 10 above.

In some embodiments, PRBs in the first frequency domain measurement set MR_Set1 may partially overlap with PRBs in the second frequency domain measurement set MR_Set2. For example, MR_Set1 may include PRBs {0, 2, 4, 6, 7, 8, 9, 10, 11} and MR_Set2 may include PRBs {7, 8, 9, 10, 11, 13, 15 , 17}, where PRBs {7, 8, 9, 10, 11} are common to both sets.

In another embodiment, MR_Set1 may include all PRBs within the system bandwidth and may be applied to the first set of ports in the CSI-RS resource set CSI-RS_Resource_Set1. The second measurement constraint set MR_Set2 may include a subset of PRBs, and may be applied to a second set of ports in the CSI-RS resource set CSI-RS_Resource_Set2. An example is shown in FIG. 15 .

15 illustrates an example of CSI-RS transmission in which one set of ports are transmitted on all PRBs and another set of ports are transmitted on a constrained set of PRBs, according to certain embodiments. The resource element grid shown in FIG. 15 includes a part of a subframe 10 having two PRBs 16 . CSI-RS ports 15 to 22 are transmitted on both PRBs 16 , while CSI-RS ports 23 to 38 are transmitted on even PRBs 16 .

)로 UE를 구성한다. 수학식 10의 새로운 CSI-RS 기준 번호는 다음과 같이 수정된다 :In some embodiments, the eNB RRC is configured with K sets of frequency domain measurement constraint parameters MR_Setk applied to the k-th set of ports in the k-th CSI-RS resource set CSI-RS_Resource_Setk (where:

) to configure the UE. The new CSI-RS reference number in Equation 10 is modified as follows:

In addition, the RE-to-port mapping formula of Equation 13 is modified as follows, where the new CSI-RS resource number i'' in the k-th CSI-RS resource set is mapped to the PRB index m.

In some embodiments, CSI-RS port sets are RRC configured for the UE instead of a CSI-RS resource set. For example, if CSI-RS_port_set1 = {15-30} and CSI-RS_port_set2 = {31-46}, MR_Set1 is applied to ports {15-30} and MR_Set2 is applied to ports {31-46}. A third group of exemplary embodiments includes a plurality of ZP CSI-RS subframe configurations. As shown in Table 4 above, the ZP CSI-RS for the serving cell may be configured with only a single CSI-RS-SubframeConfig parameter I _{CSI - RS} . This means that the UE can be configured with only one ZP CSI-RS in one subframe in the UE's configured ZP CSI-RS period T _{CSI - RS} .

However, as the number of CSI-RS ports increases in LTE Release 14, it is not possible to achieve a reuse factor higher than 1 for which SINR can be improved through ZP CSI-RS for CSI-RS within a single subframe. not. This is because a given PRB in a subframe contains only 40 available CSI-RS REs. If 32 of REs are used for NZP CSI-RS by one cell, only one cell can transmit NZP CSI-RS in a subframe. Therefore, in order to facilitate a higher reuse factor for which SINR can be improved through ZP CSI-RS, in this embodiment, the UE has one NZP CSI-RS in the CSI process and one NZP CSI-RS in the CSI process. RRC may be configured with ZP CSI-RSs occurring in a plurality of subframes within the ZP CSI-RS period. This may include configuring the UE with first and second zero power CSI-RSs occurring in the first and second subframes, wherein at least one of the first and second CSI-RSs is P It has a periodicity of subframes, and the first and second subframes are distinguished within the period P.

16 shows an example of configuring a plurality of ZP CSI-RS subframes according to an embodiment. More specifically, FIG. 16 shows an example of three cells in which CSI-RS is configured in different subframes.

For each cell, two ZP CSI-RSs are also configured in subframes and REs in which the CSI-RS of the other two cells are configured. For example, the ZP CSI-RS for cell 1 is consistent with the CSI-RS of cells 2 and 3, in subframes n+i, n+k, n+i+P, and n+k+P. is composed The first ZP CSI-RS for cell 1 is composed of subframes n+i, n+i+P, ..., and the second ZP CSI-RS is composed of subframes n+k, n+k It consists of +P, .... In this case, the periodicity of the two ZP CSI-RSs is the same. If different periods are configured for CSI-RS in three cells, P may also be different for ZP CSI-RS.

Certain embodiments include the RRC configuring the UE with a plurality of ZP CSI-RS subframe configurations. In a further embodiment, the UE is RRC configured with a plurality of configuration pairs, wherein each pair includes a ZP CSI-RS resource configuration corresponding to a ZP CSI-RS subframe configuration within the pair. Through these embodiments, the network may configure the UE with ZP CSI-RS in a plurality of subframes in which the ZP CSI-RS occupies the same REs as NZP CSI-RS for other UEs. In this way, the eNB transmitting to the UE does not need to transmit the interfering NZP CSI-RS in the PDSCH or NZP CSI-RS for other UEs, thus avoiding interference with the NZP CSI-RS for other UEs. This will facilitate a plurality of serving cells to transmit NZP CSI-RS with a large number of ports (ie, 32 ports) while avoiding interference with the NZP CSI-RS of neighboring cells.

The examples described with respect to FIGS. 12-16 may be represented by the flow diagrams of FIGS. 17 (relating to a network node) and FIG. 18 (relating to a wireless device) generally.

17 is a flowchart illustrating an exemplary method in a network node for transmitting a CSI-RS, in accordance with some embodiments. In certain embodiments, one or more steps of FIG. 17 may be performed by the network node 120 of the wireless network 100 described with respect to FIG. 12 .

The method begins at step 1712, where the network node may obtain an indication of a subset of PRBs that the wireless device should use to measure CSI-RS. For example, network node 120 may obtain an indication of a subset of PRBs that wireless device 110 may use to measure CSI-RS.

Obtaining the indication may include retrieving the predetermined indication from a memory, receiving signaling from another component of the network 100 , or any other suitable configuration. The specific indication may be determined based on factors such as deployment scenario and load conditions.

At step 1714 , the network node sends to the wireless device an indication of the subset of PRBs that the wireless device should use to measure the CSI-RS. For example, network node 120 may send to wireless device 110 an indication of a subset of PRBs that wireless device 110 should use to measure CSI-RS. The transmission may include RRC signaling, or any other suitable communication between the network node 120 and the wireless device 100 .

The representation of the subset of PRBs may include various formats, such as the format described above with respect to FIGS. 13-16 . For example, the format may include a bit map, odd/even values, density and comb offset, an index identifying a particular one of a group of formats known to the wireless device, and the like. In some embodiments, this indication may include a number of subframes that the wireless device 110 should use to measure the CSI-RS.

At step 1716, the network node transmits a CSI-RS on the indicated subset of PRBs. For example, the network node 120 may transmit the CSI-RS in PRBs that the network node 120 previously indicated to the wireless device 110 .

At step 1718 , the network node may receive, from the wireless device, measured channel state information based on one or more of the transmitted CSI-RS ports. For example, the wireless device 110 may determine the CSI based on measurements of one or more of the transmitted CSI-RSs and may transmit the CSI back to the network node 120 .

For method 1700, modifications, additions, or omissions may be made. Additionally, one or more steps of method 1700 of FIG. 17 may be performed in parallel or in any suitable order. The steps of method 1700 may be repeated over time if necessary.

18 is a flow diagram illustrating an example method at a wireless device receiving a CSI-RS, in accordance with some embodiments. In certain embodiments, one or more steps of FIG. 18 may be performed by the wireless device 110 of the wireless network 100 described with respect to FIG. 12 .

The method begins at step 1812 in which the wireless device receives an indication of a subset of PRBs that it should use to measure CSI-RS. For example, the wireless device 110 may receive, from the network node 120 , an indication of the subset of PRBs that the wireless device 110 should use to measure the CSI-RS. This indication may include any of the indications described above with respect to FIGS. 13-16 (eg, the indication sent in step 1714 of FIG. 17 ).

At step 1814 , the wireless device receives a CSI-RS on the indicated subset of PRBs. For example, the wireless device 110 may receive the CSI-RS on the indicated PRB 16 from the network node 120 .

At step 1816 , the wireless device may determine CSI based on the received CSI-RS. For example, the wireless device 110 may measure the CSI-RS on the indicated PRB 16 using the received indication to estimate an effective channel between the network node 120 and the wireless device 110 . In some embodiments, the wireless device 110 may measure the CSI-RS over a plurality of subframes.

At step 1818 , the wireless device may transmit CSI to the network node. For example, the wireless device 110 may transmit CSI to the network node 120 .

For method 1800, modifications, additions, or omissions may be made. Additionally, one or more steps of method 1800 of FIG. 18 may be performed in parallel or in any suitable order. The steps of method 1800 may be repeated over time if necessary.

19A is a block diagram illustrating an exemplary embodiment of a wireless device. The wireless device is an example of the wireless device 110 shown in FIG. 12 . In a particular embodiment, the wireless device may receive an indication of the subset of PRBs that the wireless device should use to measure the CSI-RS and receive the CSI-RS on the indicated subset of PRBs. In a particular embodiment, the wireless device may measure the received CSI-RS port to estimate an effective channel and determine the CSI to transmit the CSI to the network node.

Specific examples of wireless devices include mobile phones, smart phones, personal digital assistants (PDAs), portable computers (eg, laptops, tablets), sensors, modems, machine type (MTC) devices/machine-to-machine (M2M) devices. Provides devices, laptop embedded equipment (LEE), laptop mounted equipment (LME), USB dongle, device-to-device enabled device, vehicle-to-vehicle device, or wireless communication any other device capable of The wireless device includes processing circuitry 1900 . The processing circuit 1900 includes a transceiver 1910 , a processor 1920 , a memory 1930 , and a power supply 1940 . In some embodiments, the transceiver 1910 facilitates transmitting (eg, via an antenna) wireless signals to and receiving wireless signals from the wireless network node 120, and the processor 1920 is a wireless The device executes instructions that provide some or all of the functionality described herein provided by the device, and the memory 1930 stores instructions that are executed by the processor 1920 . Power supply 1940 powers one or more of the components of wireless device 110 , such as transceiver 1910 , processor 1920 , and/or memory 1930 .

Processor 1920 includes any suitable combination of hardware and software implemented in one or more integrated circuits or modules to execute instructions and manipulate data to perform some or all of the described functions of the wireless device. In some embodiments, processor 1920 may include, for example, one or more computers, one or more programmable logic devices, one or more central processing units (CPUs), one or more microprocessors, one or more applications, and/or other logic , and/or any suitable combination thereof. The processor 1920 may include analog and/or digital circuitry configured to perform some or all of the described functions of the wireless device 110 . For example, processor 1920 may include resistors, capacitors, inductors, transistors, diodes, and/or any other suitable circuit components.

Memory 1930 is generally operable to store computer-executable code and data. Examples of memory 1930 include computer memory (eg, random access memory (RAM) or read only memory (ROM)), mass storage media (eg, hard disk), removable storage media (eg, CD (Compact Disk) or DVD (Digital Video Disk)), and/or any other volatile or nonvolatile, non-transitory computer-readable and/or computer-executable memory device that stores information.

Power supply 1940 is generally operable to supply power to components of wireless device 110 . Power source 1940 includes any suitable type of battery, such as lithium ion, lithium air, lithium polymer, nickel cadmium, nickel metal hydride, or any other suitable type of battery for powering a wireless device. can do.

In a particular embodiment, the processor 1920 in communication with the transceiver 1910 receives an indication of a subset of PRBs that the wireless device should use to measure the CSI-RS, and CSI-RS on the indicated subset of PRBs. receive In a particular embodiment, the processor 1920 in communication with the transceiver 1910 may measure the received CSI-RS to estimate an effective channel and transmit the CSI to the network node.

Another embodiment of the wireless device is responsible for providing certain aspects of the wireless device functionality, including any of the functionality described above and/or any additional functionality (including any functionality necessary to support the solution described above). It may include additional components (other than those shown in FIG. 19A ).

19B is a block diagram illustrating example components of wireless device 110 . The components may include a receive module 1950 , a measurement module 1952 , and a transmit module 1954 .

The reception module 1950 may perform a reception function of the wireless device 110 . For example, the receiving module 1950 may receive an indication of a subset of PRBs that the wireless device should use to measure the CSI-RS, in any example described with respect to FIGS. 12-18 . CSI-RS may be received on the indicated subset of PRBs. In certain embodiments, the receiving module 1950 may include the processor 1920 or may be included in the processor 1920 . In a particular embodiment, the receiving module 1950 may communicate with the measuring module 1952 and the sending module 1954 .

The measurement module 1952 may perform a measurement function of the wireless device 110 . For example, the measurement module 1952 may estimate a radio channel using the received CSI-RS. The measurement module 1952 may determine the CSI based on the estimate. In certain embodiments, the measurement module 1952 includes or may be included in the processor 1920 . In certain embodiments, the measurement module 1952 may communicate with the receive module 1950 and the transmit module 1954 .

The transmission module 1954 may perform a transmission function of the wireless device 110 . For example, the transmission module 1954 may transmit the CSI to the network node 120 . In certain embodiments, the transport module 1954 may include or may be included in the processor 1920 . In a particular embodiment, the transmit module 1954 may communicate with the receive module 1950 and the measurement module 1952 .

20A is a block diagram illustrating an exemplary embodiment of a network node. The network node is an example of the network node 120 shown in FIG. 12 . In a particular embodiment, the network node: obtains an indication of a subset of physical resource blocks (PRBs) that the wireless device should use to measure the CSI-RS; send to the wireless device an indication of a subset of PRBs that the wireless device should use to measure the CSI-RS; CSI-RS may be transmitted on the indicated subset of PRBs.

Network node 120 may include an eNodeB, NodeB, base station, wireless access point (eg, Wi-Fi access point), low power node, base transceiver station (BTS), transmission point or node, remote RF unit (RRU), It may be a remote radio head (RRH), or other radio access node. The network node includes processing circuitry 2000 . The processing circuit 2000 includes at least one transceiver 2010 , at least one processor 2020 , at least one memory 2030 , and at least one network interface 2040 . Transceiver 2010 facilitates sending wireless signals to and receiving wireless signals from, such as wireless device 110 (eg, via an antenna); The processor 2020 executes instructions to provide some or all of the aforementioned functionality provided by the network node 120 ; memory 2030 stores instructions to be executed by processor 2020; Network interface 2040 communicates signals to backend network components such as gateways, switches, routers, the Internet, Public Switched Telephone Network (PSTN), controllers, and/or other network nodes 120 . Processor 2020 and memory 2030 may be of the same type as described with respect to processor 1920 and memory 1930 of FIG. 19A above.

In some embodiments, network interface 2040 is communicatively coupled to processor 2020 , receives input to network node 120 , transmits output from network node 120 , input or output or to any suitable device that is operable to perform both appropriate processing and to perform other devices, or any combination thereof. Network interface 2040 includes suitable hardware (eg, ports, modems, network interface cards, etc.) and software, including protocol conversion and data processing capabilities, for communicating over a network.

In a particular embodiment, the processor 2020 in communication with the transceiver 2010 is configured to: obtain an indication of a subset of PRBs that the wireless device should use to measure CSI-RS; send to the wireless device an indication of a subset of PRBs that the wireless device should use to measure the CSI-RS; operable to transmit CSI-RS on the indicated subset of PRBs.

Another embodiment of the network node 120 is to provide certain aspects of the network node, including any of the functionality described above and/or any additional functionality (including any functionality necessary to support the solution described above). It includes additional components (other than those shown in FIG. 20A) that are responsible for it. Various different types of network nodes may include components that have the same physical hardware but are configured (eg, via programming) to support different radio access technologies, or may represent partially or completely different physical components.

20B is a block diagram illustrating exemplary components of network node 120 . The components may include an acquiring module 2050 , a sending module 2052 , and a receiving module 2054 .

The acquisition module 2050 may perform an acquisition function of the network node 120 . For example, the obtaining module 2050 may obtain an indication of the subset of PRBs that the wireless device should use to measure the CSI-RS according to any one of the examples described in connection with FIGS. 12-18 . have. In certain embodiments, the acquiring module 2050 includes or may be included in the processor 2020 . In a particular embodiment, the acquiring module 2050 may communicate with the sending module 2052 and the receiving module 2054 .

The transmission module 2052 may perform a transmission function of the network node 120 . For example, the transmitting module 2052 may transmit an indication of a subset of PRBs that the wireless device should use to measure the CSI-RS, one according to any example described with respect to FIGS. 12-18 . CSI-RS may be transmitted on the above PRBs. In certain embodiments, the transport module 2052 includes or may be included in the processor 2020 . In a particular embodiment, the sending module 2052 may communicate with the acquiring module 2050 and the receiving module 2054 .

The reception module 2054 may perform a reception function of the network node 120 . For example, the receiving module 2054 may receive the CSI from the wireless device 110 . In certain embodiments, the receiving module 2054 may include or may be included in the processor 1920 . In a particular embodiment, the receiving module 2054 may communicate with the acquiring module 2050 and the sending module 2052 .

Modifications, additions, or omissions may be made to the systems and apparatus disclosed herein without departing from the scope of the invention. Components of systems and devices may be integrated or separate. In addition, operations of systems and apparatus may be performed by more, fewer, or other components. Additionally, operation of the systems and apparatus may be performed using any suitable logic including software, hardware, and/or other logic. As used herein, "each" refers to each member of a set, or each member of a subset of a set.

Modifications, additions, or omissions may be made to the methods disclosed herein without departing from the scope of the invention. Methods may include more, fewer, or other steps. Additionally, the steps may be performed in any suitable order.

Although the present disclosure has been described in terms of certain embodiments, changes and permutations of the embodiments will be apparent to those skilled in the art. Accordingly, the above description of the embodiments does not limit the present disclosure. Other changes, substitutions, and alterations are possible without departing from the scope of the present disclosure, as defined by the following claims.

Certain embodiments may be implemented within the framework of a particular communication standard. The example below provides a non-limiting example of how the proposed solutions can be implemented within the framework of the 3GPP TSG RAN standard. The changes described are merely to illustrate how certain aspects of the proposed solution may be implemented in a particular standard. However, the proposed solution may also be implemented in other suitable ways, both in the 3GPP specification and in other specifications or standards.

For example, a specific standard may include the following agreement with respect to CSI-RS design for Class A eFD-MIMO. For {20, 24, 28, 32} ports, the CSI-RS resource for class A CSI reporting may include an aggregation of K CSI-RS configurations [ie, RE patterns]. The number of REs in the k-th configuration is N _k ∈ {4, 8}. The same N _k = N can be used for all k. The following are not excluded: (a) CSI-RS density per port per PRB = 1; (b) Different CSI-RS densities per port for different CSI-RS ports.

Specific examples include TDM. The UE may measure and report one set of ports in one subframe and the remaining set of ports may measure and report in another subframe. The challenge of this scheme is how the eNB combines the CSI reports measured on different sets of CSI-RS ports on different subframes. Also, if CSI corresponding to different sets of CSI-RS ports is measured/reported on different CSI-RS subframes, the reported CSI may be adversely affected by frequency drift/Doppler across the subframes. Simulation results at 24 ports indicate that the TDM-based scheme can suffer from link throughput loss of 10-20% compared to the FDM scheme with an SNR range of 0-10 dB.

Regarding the overhead of the TDM scheme, the TDM scheme does not reduce the CSI-RS overhead over one CSI-RS transmission period. This is illustrated by a comparison between the TDM scheme and the CSI-RS scheme, where all ports are measured in a single subframe in FIGS. 21A and 21B .

In FIG. 21A , a CSI-RS design based on a TDM scheme for 32 ports is shown, where CSI ports 15 to 30 are measured in subframes (k+1), and CSI ports 31 to 46 are subframes ( k+2). Assuming a system having two CRS ports, three OFDM symbols for PDCCH, two DMRS ports, and a CSI-RS period Np = 5 ms, the CSI-RS overhead of the TDM scheme over one CSI-RS period is about 6%.

Under the same assumption, the scheme of FIG. 21B in which all 32 ports are measured in a subframe (k + 1) achieves the same CSI-RS overhead of 6%. From this comparison, it is clear that the TDM scheme simply distributes the overhead over different subframes without reducing the CSI-RS overhead.

In some embodiments, the TDM scheme may be down-selected because it simply distributes the CSI-RS overhead over different subframes without reducing the CSI-RS overhead.

Specific examples include FDM. The UE may be configured to measure channels on a subset of CSI-RS ports on one fixed set of PRBs and another subset of antenna ports on a different fixed set of PRBs. An example of a 32-port is shown in FIG. 14 . In this example, CSI-RS ports 15-30 are transmitted on even PRBs and CSI-RS ports 31-46 are transmitted on odd PRBs.

Evaluating the performance of the FDM scheme may include system-level simulation using a 32-port 8x4 dual polarized array with 2x1 subarray virtualization. The performance of the FDM scheme with a CSI-RS density of 0.5 RE/RB/port can be compared with the performance of a CSI-RS design with a full density (ie, 1 RE/RB/port). The results of the 3D-UMi and 3D-UMa scenarios are provided in Tables 5 and 6, respectively. From these results, a 32-port CSI-RS resource can be achieved by aggregating four 8-port CSI-RS configurations with CDM-4 and 3dB power boosting.

[Table 5]

Performance comparison in 3D-UMi

[Table 6]

Performance comparison in 3D-Uma

These results show that the FDM scheme achieves a small average throughput gain of 2% at a very low resource utilization of 5% due to the lower overhead advantage compared to the full-density CSI-RS scheme. However, at higher resource utilization, the FDM scheme suffers from significant throughput loss. At 50% RU, the cell edge performance of the FDM scheme is 25% (for 3D-UMi) and 53% (for 3D-UMa) lower than the full-density CSI-RS scheme. This loss is primarily due to the reduced processing gain associated with the FDM scheme compared to the full-density CSI-RS scheme.

The FDM scheme with 0.5 RE/RB/port achieves small gains at very light loads, but suffers from significant losses at medium to high loads compared to CSI-RS designs with a density of 1 RE/RB/port. Therefore, given the results of Tables 5 and 6, an FDM-based design with a fixed CSI-RS density may not be a good solution because of its low performance at high loads. Sufficient configurability in the CSI-RS design to also have a CSI-RS density per port of 1 RE/RB/port in addition to a CSI-RS density lower than 1 RE/RB/port to ensure good performance in medium to high load conditions this should be allowed

FDM-based CSI-RS design with fixed CSI-RS density may not be considered for Class A eFD-MIMO. Sufficient configurability should be allowed in the CSI-RS design to have a CSI-RS density per port of 1 RE/RB/port in addition to the CSI-RS density lower than 1 RE/RB/port.

Certain embodiments include measurement constraints in the frequency domain. Since it is one of the objectives of the eFD-MIMO standard to specify enhancement of {20, 24, 28, 32} CSI-RS port by a mechanism for reducing overhead for CSI-RS transmission, a more flexible approach is It is to allow the density design of -RS to be configurable. This may be achieved via a measurement constraint (MR) in the frequency domain where the UE may be asked to measure a channel on a configurable set of PRBs. CSI-RS is transmitted only in PRBs in which the UE is requested to perform channel measurement. The MR in the frequency domain may be configured semi-statically and may be RRC signaled to the UE.

Because MR in the frequency domain is configurable, the density of CSI-RS ports can be flexibly selected according to the deployment scenario. For example, in the case of a low load, low delay spread condition, CSI-RS ports may be configured with reduced density. For high load and/or high delay spread conditions, a higher density can be configured for the CSI-RS ports to avoid the performance loss shown in the results in Tables 5 and 6.

Several alternatives can be achieved for reducing the CSI-RS density per port via MR in the frequency domain. Some examples include:

FDM: By MR in the frequency domain, FDM schemes with different CSI-RS densities can be achieved. For example, the 32 port reduced density CSI-RS example of FIG. 14 shows that the UE measures CSI-RS ports 15-30 on PRBs 0, 2, 4, 6, ... and PRBs 1, 3, 5, 7, ... can be achieved by configuring to measure CSI-RS ports 31 to 46. If this density reduction factor is suitable for a given deployment scenario, another density reduction factor (ie 3 or 4) in MR in the frequency domain can also be configured.

Partial overlap: A partially overlapping CSI-RS design can be achieved with MR in the frequency domain. Considering the example of 32-port given in FIG. 15 , the UE is configured to measure CSI-RS ports 23 to 38 only on PRBs 1, 3, 5, 7, .... For CSI-RS ports 15 to 22, the UE is configured to measure CSI-RS on all PRBs.

Partial bandwidth measurement: MR in the frequency domain can be effectively used to probe a UE to measure CSI-RS only in one or more subbands in the context of aperiodic CSI-RS.

Overall CSI-RS Density: By configuring the UE to measure CSI-RS on all PRBs, a CSI-RS density per port of 1 RE/port/PRB can be achieved through MR in the frequency domain.

MR in the frequency domain may be applied to a case with different CSI-RS resources with a different number of ports and a case involving a different CDM design.

Given these advantages, certain embodiments provide measurement constraints in the frequency domain that are used to achieve many alternatives for reducing per-port CSI-RS density, including FDM, partial overlap, partial bandwidth, and total CSI-RS density. includes For class A eFD-MIMO, measurement constraints in the frequency domain provide good flexibility in configuring the density of CSI-RS according to deployment scenarios and load conditions.

Some embodiments include CSI-RS SINR enhancements. The performance of a 32-port CSI-RS design with CDM-4 and 3dB power boosting (9dB gain) can be compared to the upper bound performance of a 32-port CSI-RS design with 15dB gain. In both cases, assume a CSI-RS density of 1 RE/RB/port and a 32 port 8x4 dual polarized array with 2x1 subarray virtualization. Detailed simulation parameters are given above.

Table 7 shows the 3D-UMi and 3D-UMa scenario results at 50% resource utilization. These results show a cell-edge throughput upper bound gain of 29 to 41% when using a 15 dB gain compared to a case with a 9 dB gain. The corresponding average throughput gain ranges from 11 to 12%. This implies that more gains are possible if the CSI-RS SINR can be further improved.

[Table 7]

Performance comparison between 9 dB and 15 dB gain cases at 50% reference RU

Abbreviations used in the previous description include:

3GPP Third Generation Partnership Project

AP Access Point

BSC Base Station Controller

BTS Base Transceiver Station

CDM Code Division Multiplexing

CPE Customer Premises Equipment

CRS Cell Specific Reference Signal

CQI Channel Quality Indicator

CSI Channel State Information

CSI-RS Channel State Information Reference Signal

D2D Device to Device

DAS Distributed Antenna System

DCI Downlink Control Information

DFT Discrete Fourier Transform

DL Downlink

DMRS Demodulation Reference Signal

eNB eNodeB

EPDCCH Enhanced Physical Downlink Control Channel

FDD Frequency Division Duplex

LTE Long Term Evolution

LAN Local Area Network

LEE Laptop Embedded Equipment

LME Laptop Mounted Equipment

MAC Medium Access Control

M2M Machine to Machine

MIMO Multi-Input Multi-Output

MR Measurement Restriction

MTC Machine Type Communication

NR New Radio

NZP Non-Zero Power

OCC Orthogonal Cover Code

OFDM Orthogonal Frequency Division Multiplexing

PDCCH Physical Downlink Control Channel

PDSCH Physical Downlink Shared Channel

PMI Precoded Matrix Indicator

PRB Physical Resource Block

PSTN Public Switched Telephone Network

PUSCH Physical Uplink Shared Channel

PUCCH Physical Uplink Control Channel

RAN Radio Access Network

RAT Radio Access Technology

RB resource block (Resource Block)

RBS Radio Base Station

RE Resource Element

RI Rank Indicator

RNC Radio Network Controller

RRC Radio Resource Control

RRH Radio Resource Head (Remote Radio Head)

RRU Remote Radio Unit

TDD Time-Division Duplex

TFRE Time Frequency Resource Element

TM Transmission Mode

UE User Equipment

UL Uplink

UTRAN Universal Terrestrial Radio Access Network

WAN Wireless Access Network

ZP Zero Power

Claims (48)

A method for use in a network node transmitting channel state information reference signals (CSI-RS), comprising:
sending 1714 to the wireless device an indication of a subset of physical resource blocks (PRBs) that the wireless device should use to measure the CSI-RS, each CSI-RS associated with an antenna port and the subset of PRBs includes a subset of system bandwidth; and
Transmitting CSI-RS on the indicated subset of PRBs (1716)
including,
The network node transmits CSI-RS on a total number of antenna ports by using the subset of PRBs, and each PRB in the subset of PRBs performs CSI-RS mapping for the total number of antenna ports. includes,
wherein the indication of the subset of PRBs that the wireless device should use to measure CSI-RS comprises a density value and a comb offset. delete delete delete delete delete delete delete delete delete delete A method for use in a wireless device that receives channel state information reference signals (CSI-RSs), the method comprising:
Receiving 1812 an indication of a subset of physical resource blocks (PRBs) that the wireless device should use to measure CSI-RS, each CSI-RS associated with an antenna port, the subset of PRBs contains a subset of the system bandwidth—; and
Receiving CSI-RS on the indicated subset of PRBs ( 1814 )
including,
The wireless device receives a CSI-RS transmitted on a total number of antenna ports using the subset of PRBs from a network node, and each PRB in the subset of PRBs is for the total number of antenna ports. Includes CSI-RS mapping,
wherein the indication of the subset of PRBs that the wireless device should use to measure CSI-RS comprises a density value and a comb offset. delete delete delete delete delete delete delete delete delete delete delete A network node (120) operable to transmit a channel state information reference signal (CSI-RS) (135), the network node comprising a processing circuitry (2000), the processing circuitry comprising:
transmit to the wireless device an indication of a subset of physical resource blocks (PRBs) that the wireless device should use to measure CSI-RS, each CSI-RS associated with an antenna port, the subset of PRBs being contains a subset of the system bandwidth—;
operable to transmit CSI-RS on a subset of the indicated PRBs;
The network node transmits CSI-RS on a total number of antenna ports by using the subset of PRBs, and each PRB in the subset of PRBs performs CSI-RS mapping for the total number of antenna ports. includes,
and the indication of the subset of PRBs that the wireless device should use to measure CSI-RS comprises a density value and a comb offset. 25. The network node of claim 24, wherein the processing circuitry is further operable to obtain an indication of the subset of PRBs that the wireless device should use to measure CSI-RS. delete 26. The network node of claim 24 or 25, wherein the subset of PRBs that the wireless device should use to measure CSI-RS comprises even numbered PRBs. 26. The network node of claim 24 or 25, wherein the subset of PRBs that the wireless device should use to measure CSI-RS comprises odd numbered PRBs. delete 26. The method of claim 24 or 25, wherein the density value comprises a density of one-half;
The first comb offset indicates that the wireless device should use PRBs in set m1 to measure CSI-RS, wherein the set m1 is

includes;
The second comb offset indicates that the wireless device should use PRBs in set m2 to measure CSI-RS, wherein set m2 is

comprising, a network node. 26. The method of claim 24 or 25, wherein the density value comprises a density of 1/3;
The first comb offset indicates that the wireless device should use PRBs in set m1 to measure CSI-RS, wherein the set m1 is

includes;
The second comb offset indicates that the wireless device should use PRBs in set m2 to measure CSI-RS, wherein set m2 is

includes;
The third comb offset indicates that the wireless device should use PRBs in set m3 to measure CSI-RS, wherein set m3 is

comprising, a network node. 26. The method of claim 24 or 25, wherein the indication of the subset of PRBs that the wireless device should use to measure CSI-RS comprises an index value k, wherein the index value k comprises a plurality of values stored in the wireless device. A network node, referencing one of the representations. 26. The method of claim 24 or 25, wherein the indication of the subset of PRBs that the wireless device should use to measure CSI-RS is a continuous CSI-RS subframe in which the wireless device should measure CSI-RS. A network node, further comprising a number of 26. The method of claim 24 or 25, wherein the processing circuitry is further operative to receive, from the wireless device, channel state information (CSI) determined based on a measurement of one or more of the transmitted CSI-RSs. Possible, network node. A wireless device (110) operable to receive a channel state information reference signal (CSI-RS) (135), the wireless device comprising: processing circuitry (1900), the processing circuitry comprising:
Receive an indication of a subset of physical resource blocks (PRBs) that the wireless device should use to measure CSI-RS, each CSI-RS associated with an antenna port, the subset of PRBs being a portion of the system bandwidth including a subset—;
operable to receive CSI-RS on a subset of the indicated PRBs;
The wireless device receives a CSI-RS transmitted on a total number of antenna ports using the subset of PRBs from a network node, and each PRB in the subset of PRBs is for the total number of antenna ports. Includes CSI-RS mapping,
and the indication of the subset of PRBs that the wireless device should use to measure CSI-RS comprises a density value and a comb offset. 36. The method of claim 35, wherein the processing circuitry is further configured to: determine channel state information (CSI) based on the received CSI-RS; and transmit the CSI to a network node. delete 36. The wireless device of claim 35, wherein the total number of antenna ports is greater than 16. 37. The wireless device of claim 35 or 36, wherein the subset of PRBs that the wireless device should use to measure CSI-RS comprises even numbered PRBs. 37. The wireless device of claim 35 or 36, wherein the subset of PRBs that the wireless device should use to measure CSI-RS comprises odd numbered PRBs. delete 37. The method of claim 35 or 36, wherein the density value comprises a density of one-half;
The first comb offset indicates that the wireless device should use PRBs in set m1 to measure CSI-RS, wherein the set m1 is

includes;
The second comb offset indicates that the wireless device should use PRBs in set m2 to measure CSI-RS, wherein set m2 is

A wireless device comprising: 37. The method of claim 35 or 36, wherein the density value comprises a density of 1/3;
The first comb offset indicates that the wireless device should use PRBs in set m1 to measure CSI-RS, wherein the set m1 is

includes;
The second comb offset indicates that the wireless device should use PRBs in set m2 to measure CSI-RS, wherein set m2 is

includes;
The third comb offset indicates that the wireless device should use PRBs in set m3 to measure CSI-RS, wherein set m3 is

A wireless device comprising: 37. The method of claim 35 or 36, wherein the indication of the subset of PRBs that the wireless device should use to measure CSI-RS comprises an index value k, wherein the index value k comprises a plurality of values stored in the wireless device. A wireless device that refers to one of the indications. 39. The method of claim 38, wherein the indication of the subset of PRBs that the wireless device should use to measure CSI-RS further adds a number of consecutive CSI-RS subframes for which the wireless device should measure CSI-RS. comprising a wireless device. 46. The wireless device of claim 45, wherein the processing circuitry is further operable to determine channel state information (CSI) based on a CSI-RS received over the number of consecutive CSI-RS subframes. delete delete

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